From: Benjamin Auder <benjamin.auder@somewhere>
Date: Thu, 11 Nov 2021 18:22:59 +0000 (+0100)
Subject: First commit
X-Git-Url: https://git.auder.net/js/current/pieces/cq.svg?a=commitdiff_plain;h=41534b92f0bcfc8ef5f58d8040706a5e7ce088c6;p=xogo.git

First commit
---

41534b92f0bcfc8ef5f58d8040706a5e7ce088c6
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..490dce9
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,9 @@
+*.swp
+*~
+*.min.js
+*.min.css
+/node_modules/
+/assets/
+/assets.zip
+/.pid
+/parameters.js
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..bd404c0
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,15 @@
+ISC license https://opensource.org/licenses/ISC
+
+Copyright (C) 2021-2022 Benjamin Auder
+
+Permission to use, copy, modify, and/or distribute this software for any
+purpose with or without fee is hereby granted, provided that the above
+copyright notice and this permission notice appear in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..1f81c9d
--- /dev/null
+++ b/README.md
@@ -0,0 +1,19 @@
+# xogo.live
+
+Simplified version of old vchess.club, to focus on the essential : the game.
+
+## Requirements (dev)
+
+Global npm install: nodemon, livereload. <br>
+A static web server like "php -S localhost:8000".
+
+## Usage
+
+```wget https://xogo.live/assets.zip && unzip assets.zip``` <br>
+Rename parameters.js.dist &rarr; parameters.js, and edit file. <br>
+```npm i```
+
+```./start.sh``` <br>
+```php -S localhost:PORT``` (or other static server) <br>
+... <br>
+```./stop.sh```
diff --git a/TODO b/TODO
new file mode 100644
index 0000000..c0761e6
--- /dev/null
+++ b/TODO
@@ -0,0 +1,8 @@
+Dark Racing Kings ?
+Checkered-Teleport ?
+
+// TODO: playvisual enlightened test (pas forcément mode dark...)
+
+// rem ref to bordContainer --> rethink CSS design...
+
+// TODO: Otage, Emergo, Pacosako : fonction "buildPiece(arg1, arg2)" returns HTML element with 2 SVG or SVG + number
diff --git a/app.js b/app.js
new file mode 100644
index 0000000..f897062
--- /dev/null
+++ b/app.js
@@ -0,0 +1,424 @@
+let $ = document; //shortcut
+
+///////////////////
+// Initialisations
+
+// https://stackoverflow.com/a/27747377/12660887
+function dec2hex (dec) { return dec.toString(16).padStart(2, "0") }
+function generateId (len) {
+  var arr = new Uint8Array((len || 40) / 2)
+  window.crypto.getRandomValues(arr)
+  return Array.from(arr, dec2hex).join('')
+}
+
+// Populate variants dropdown list
+let dropdown = $.getElementById("selectVariant");
+dropdown[0] = new Option("? ? ?", "_random", true, true);
+dropdown[0].title = "Random variant";
+for (let i = 0; i < variants.length; i++) {
+  let newOption = new Option(
+    variants[i].disp || variants[i].name, variants[i].name, false, false);
+  newOption.title = variants[i].desc;
+  dropdown[dropdown.length] = newOption;
+}
+
+// Ensure that I have a socket ID and a name
+if (!localStorage.getItem("sid"))
+  localStorage.setItem("sid", generateId(8));
+if (!localStorage.getItem("name"))
+  localStorage.setItem("name", "@non" + generateId(4));
+const sid = localStorage.getItem("sid");
+$.getElementById("myName").value = localStorage.getItem("name");
+
+/////////
+// Utils
+
+function setName() {
+  localStorage.setItem("name", $.getElementById("myName").value);
+}
+
+// Turn a "tab" on, and "close" all others
+function toggleVisible(element) {
+  for (elt of document.querySelectorAll('body > div')) {
+    if (elt.id != element) elt.style.display = "none";
+    else elt.style.display = "block";
+  }
+}
+
+let seek_vname;
+function seekGame() {
+  seek_vname = $.getElementById("selectVariant").value;
+  send("seekgame", {vname: seek_vname, name: localStorage.getItem("name")});
+  toggleVisible("pendingSeek");
+}
+function cancelSeek() {
+  send("cancelseek", {vname: seek_vname});
+  toggleVisible("newGame");
+}
+
+function sendRematch() {
+  send("rematch", { gid: gid });
+  toggleVisible("pendingRematch");
+}
+function cancelRematch() {
+  send("norematch", { gid: gid });
+  toggleVisible("newGame");
+}
+
+// Play with a friend (or not ^^)
+function showNewGameForm() {
+  const vname = $.getElementById("selectVariant").value;
+  if (vname == "_random") alert("Select a variant first");
+  else {
+    $.getElementById("gameLink").innerHTML = "";
+    $.getElementById("selectColor").selectedIndex = 0;
+    toggleVisible("newGameForm");
+    import(`/variants/${vname}/class.js`).then(module => {
+      const Rules = module.default;
+      prepareOptions(Rules);
+    });
+  }
+}
+function backToNormalSeek() { toggleVisible("newGame"); }
+
+function toggleStyle(e, word) {
+  options[word] = !options[word];
+  e.target.classList.toggle("highlight-word");
+}
+
+let options;
+function prepareOptions(Rules) {
+  options = {};
+  let optHtml = "";
+  for (let select of Rules.Options.select) {
+    optHtml += `
+      <label for="var_${select.variable}">${select.label}</label>
+      <select id="var_${select.variable}" data-numeric="1">`;
+    for (option of select.options) {
+      const defaut = option.value == select.defaut;
+      optHtml += `<option value="${option.value}"`;
+      if (defaut) optHtml += 'selected="true"';
+      optHtml += `>${option.label}</option>`;
+    }
+    optHtml += '</select>';
+  }
+  for (let check of Rules.Options.check) {
+    optHtml += `
+      <label for="var_${check.variable}">${check.label}</label>
+      <input id="var_${check.variable}"
+             type="checkbox"`;
+    if (check.defaut) optHtml += 'checked="true"';
+    optHtml += '/>';
+  }
+  if (Rules.Options.styles.length >= 1) optHtml += "<p>";
+  for (let style of Rules.Options.styles) {
+    optHtml += `
+      <span class="word" onClick="toggleStyle(event, '${style}')">
+        ${style}
+      </span>`;
+  }
+  if (Rules.Options.styles.length >= 1) optHtml += "</p>";
+  $.getElementById("gameOptions").innerHTML = optHtml;
+}
+
+function getGameLink() {
+  const vname = $.getElementById("selectVariant").value;
+  const color = $.getElementById("selectColor").value;
+  for (const select of $.querySelectorAll("#gameOptions > select")) {
+    let value = select.value;
+    if (select.attributes["data-numeric"]) value = parseInt(value, 10);
+    options[ select.id.split("_")[1] ] = value;
+  }
+  for (const check of $.querySelectorAll("#gameOptions > input"))
+    options[ check.id.split("_")[1] ] = check.checked;
+  send("creategame", {
+    vname: vname,
+    player: { sid: sid, name: localStorage.getItem("name"), color: color },
+    options: options
+  });
+}
+
+const fillGameInfos = (gameInfos, oppIndex) => {
+  fetch(`/variants/${gameInfos.vname}/rules.html`)
+  .then(res => res.text())
+  .then(txt => {
+    let htmlContent = `
+      <p>
+        <strong>${gameInfos.vdisp}</strong>
+        <span>vs. ${gameInfos.players[oppIndex].name}</span>
+      </p>
+      <hr>
+      <p>`;
+    htmlContent +=
+      Object.entries(gameInfos.options).map(opt => {
+        return (
+          '<span class="option">' +
+          (opt[1] === true ? opt[0] : `${opt[0]}:${opt[1]}`) +
+          '</span>'
+        );
+      })
+      .join(", ");
+    htmlContent += `
+      </p>
+      <hr>
+      <div class="rules">
+        ${txt}
+      </div>
+      <button onClick="toggleGameInfos()">Back to game</button>`;
+    $.getElementById("gameInfos").innerHTML = htmlContent;
+  });
+};
+
+////////////////
+// Communication
+
+let socket, gid, attempt = 0;
+const autoReconnectDelay = () => {
+  return [100, 200, 500, 1000, 3000, 10000, 30000][Math.min(attempt, 6)];
+};
+
+function copyClipboard(msg) { navigator.clipboard.writeText(msg); }
+function getWhatsApp(msg) {
+  return `https://api.whatsapp.com/send?text=${encodeURIComponent(msg)}`;
+}
+
+const tryResumeGame = () => {
+  attempt = 0;
+  // If a game is found, resume it:
+  if (localStorage.getItem("gid")) {
+    gid = localStorage.getItem("gid");
+    send("getgame", { gid: gid });
+  }
+  else {
+    // If URL indicates "play with a friend", start game:
+    const hashIdx = document.URL.indexOf('#');
+    if (hashIdx >= 0) {
+      const urlParts = $.URL.split('#');
+      gid = urlParts[1];
+      send("joingame", { gid: gid, name: localStorage.getItem("name") });
+      localStorage.setItem("gid", gid);
+      history.replaceState(null, '', urlParts[0]);
+    }
+  }
+};
+
+const messageCenter = (msg) => {
+  const obj = JSON.parse(msg.data);
+  switch (obj.code) {
+    // Start new game:
+    case "gamestart": {
+      if (!$.hasFocus()) notifyMe("game");
+      gid = obj.gid;
+      initializeGame(obj);
+      break;
+    }
+    // Game vs. friend just created on server: share link now
+    case "gamecreated": {
+      const link = `${Params.http_server}/#${obj.gid}`;
+      $.getElementById("gameLink").innerHTML = `
+        <p>
+          <a href="${getWhatsApp(link)}">WhatsApp</a>
+          /
+          <span onClick='copyClipboard("${link}")'>ToClipboard</span>
+        </p>
+        <p>${link}</p>
+      `;
+      break;
+    }
+    // Game vs. friend joined after 1 minute (try again!)
+    case "jointoolate":
+      alert("Game no longer available");
+      break;
+    // Get infos of a running game (already launched)
+    case "gameinfo":
+      initializeGame(obj);
+      break;
+    // Tried to resume a game which is now gone:
+    case "nogame":
+      localStorage.removeItem("gid");
+      break;
+    // Receive opponent's move:
+    case "newmove":
+      if (!$.hasFocus()) notifyMe("move");
+      vr.playReceivedMove(obj.moves, () => {
+        if (vr.getCurrentScore(obj.moves[obj.moves.length-1]) != "*") {
+          localStorage.removeItem("gid");
+          setTimeout( () => toggleVisible("gameStopped"), 2000 );
+        }
+        else toggleTurnIndicator(true);
+      });
+      break;
+    // Opponent stopped game (draw, abort, resign...)
+    case "gameover":
+      toggleVisible("gameStopped");
+      localStorage.removeItem("gid");
+      break;
+    // Opponent cancelled rematch:
+    case "closerematch":
+      toggleVisible("newGame");
+      break;
+  }
+};
+
+const handleError = (err) => {
+  if (err.code === 'ECONNREFUSED') {
+    removeAllListeners();
+    alert("Server refused connection. Please reload page later");
+  }
+  socket.close();
+};
+
+const handleClose = () => {
+  setTimeout(() => {
+    removeAllListeners();
+    connectToWSS();
+  }, autoReconnectDelay());
+};
+
+const removeAllListeners = () => {
+  socket.removeEventListener("open", tryResumeGame);
+  socket.removeEventListener("message", messageCenter);
+  socket.removeEventListener("error", handleError);
+  socket.removeEventListener("close", handleClose);
+};
+
+const connectToWSS = () => {
+  socket =
+    new WebSocket(`${Params.socket_server}${Params.socket_path}?sid=${sid}`);
+  socket.addEventListener("open", tryResumeGame);
+  socket.addEventListener("message", messageCenter);
+  socket.addEventListener("error", handleError);
+  socket.addEventListener("close", handleClose);
+  attempt++;
+};
+connectToWSS();
+
+const send = (code, data) => {
+  socket.send(JSON.stringify(Object.assign({code: code}, data)));
+};
+
+///////////
+// Playing
+
+function toggleTurnIndicator(myTurn) {
+  let indicator = $.getElementById("chessboard");
+  if (myTurn) indicator.style.outline = "thick solid green";
+  else indicator.style.outline = "thick solid lightgrey";
+}
+
+function notifyMe(code) {
+  const doNotify = () => {
+    // NOTE: empty body (TODO?)
+    new Notification("New " + code, { vibrate: [200, 100, 200] });
+    new Audio("/assets/new_" + code + ".mp3").play();
+  }
+  if (Notification.permission === 'granted') doNotify();
+  else if (Notification.permission !== 'denied') {
+    Notification.requestPermission().then((permission) => {
+      if (permission === 'granted') doNotify();
+    });
+  }
+}
+
+let curMoves = [];
+const afterPlay = (move) => { //pack into one moves array, then send
+  curMoves.push({
+    appear: move.appear,
+    vanish: move.vanish,
+    start: move.start,
+    end: move.end
+  });
+  if (vr.turn != color) {
+    toggleTurnIndicator(false);
+    send("newmove", { gid: gid, moves: curMoves, fen: vr.getFen() });
+    curMoves = [];
+    const result = vr.getCurrentScore(move);
+    if (result != "*") {
+      setTimeout( () => {
+        toggleVisible("gameStopped");
+        send("gameover", { gid: gid });
+      }, 2000);
+    }
+  }
+};
+
+// Avoid loading twice the same stylesheet:
+const conditionalLoadCSS = (vname) => {
+  const allIds = [].slice.call($.styleSheets).map(s => s.id);
+  const newId = vname + "_css";
+  if (!allIds.includes(newId)) {
+    $.getElementsByTagName("head")[0].insertAdjacentHTML(
+      "beforeend",
+      `<link id="${newId}" rel="stylesheet"
+             href="/variants/${vname}/style.css"/>`);
+  }
+};
+
+let vr, color;
+function initializeGame(obj) {
+  const options = obj.options || {};
+  import(`/variants/${obj.vname}/class.js`).then(module => {
+    const Rules = module.default;
+    conditionalLoadCSS(obj.vname);
+    color = (sid == obj.players[0].sid ? "w" : "b");
+    // Init + remove potential extra DOM elements from a previous game:
+    document.getElementById("boardContainer").innerHTML = `
+      <div id="upLeftInfos"
+           onClick="toggleGameInfos()">
+        <img src="/assets/icon_infos.svg"/>
+      </div>
+      <div id="upRightStop"
+           onClick="confirmStopGame()">
+        <img src="/assets/icon_close.svg"/>
+      </div>
+      <div class="resizeable" id="chessboard"></div>`;
+    vr = new Rules({
+      seed: obj.seed, //may be null if FEN already exists (running game)
+      fen: obj.fen,
+      element: "chessboard",
+      color: color,
+      afterPlay: afterPlay,
+      options: options
+    });
+    if (!obj.fen) {
+      // Game creation
+      if (color == "w") send("setfen", {gid: obj.gid, fen: vr.getFen()});
+      localStorage.setItem("gid", obj.gid);
+    }
+    const select = $.getElementById("selectVariant");
+    obj.vdisp = "";
+    for (let i=0; i<select.options.length; i++) {
+      if (select.options[i].value == obj.vname) {
+        obj.vdisp = select.options[i].text;
+        break;
+      }
+    }
+    fillGameInfos(obj, color == "w" ? 1 : 0);
+    if (obj.randvar) toggleVisible("gameInfos");
+    else toggleVisible("boardContainer");
+    toggleTurnIndicator(vr.turn == color);
+  });
+}
+
+function confirmStopGame() {
+  if (confirm("Stop game?")) {
+    send("gameover", { gid: gid, relay: true });
+    localStorage.removeItem("gid");
+    toggleVisible("gameStopped");
+  }
+}
+
+function toggleGameInfos() {
+  if ($.getElementById("gameInfos").style.display == "none")
+    toggleVisible("gameInfos");
+  else toggleVisible("boardContainer");
+}
+
+$.body.addEventListener("keydown", (e) => {
+  if (!localStorage.getItem("gid")) return;
+  if (e.keyCode == 27) confirmStopGame();
+  else if (e.keyCode == 32) {
+    e.preventDefault();
+    toggleGameInfos();
+  }
+});
diff --git a/base_pieces.css b/base_pieces.css
new file mode 100644
index 0000000..08f8257
--- /dev/null
+++ b/base_pieces.css
@@ -0,0 +1,37 @@
+/** Embedded SVGs for all chess pieces */
+piece.pawn.white {
+  background-image: url('data:image/svg+xml;base64,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');
+}
+piece.bishop.white {
+  background-image: url('data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHdpZHRoPSI0NSIgaGVpZ2h0PSI0NSI+PGcgZmlsbD0ibm9uZSIgZmlsbC1ydWxlPSJldmVub2RkIiBzdHJva2U9IiMwMDAiIHN0cm9rZS13aWR0aD0iMS41IiBzdHJva2UtbGluZWNhcD0icm91bmQiIHN0cm9rZS1saW5lam9pbj0icm91bmQiPjxnIGZpbGw9IiNmZmYiIHN0cm9rZS1saW5lY2FwPSJidXR0Ij48cGF0aCBkPSJNOSAzNmMzLjM5LS45NyAxMC4xMS40MyAxMy41LTIgMy4zOSAyLjQzIDEwLjExIDEuMDMgMTMuNSAyIDAgMCAxLjY1LjU0IDMgMi0uNjguOTctMS42NS45OS0zIC41LTMuMzktLjk3LTEwLjExLjQ2LTEzLjUtMS0zLjM5IDEuNDYtMTAuMTEuMDMtMTMuNSAxLTEuMzU0LjQ5LTIuMzIzLjQ3LTMtLjUgMS4zNTQtMS45NCAzLTIgMy0yeiIvPjxwYXRoIGQ9Ik0xNSAzMmMyLjUgMi41IDEyLjUgMi41IDE1IDAgLjUtMS41IDAtMiAwLTIgMC0yLjUtMi41LTQtMi41LTQgNS41LTEuNSA2LTExLjUtNS0xNS41LTExIDQtMTAuNSAxNC01IDE1LjUgMCAwLTIuNSAxLjUtMi41IDQgMCAwLS41LjUgMCAyeiIvPjxwYXRoIGQ9Ik0yNSA4YTIuNSAyLjUgMCAxIDEtNSAwIDIuNSAyLjUgMCAxIDEgNSAweiIvPjwvZz48cGF0aCBkPSJNMTcuNSAyNmgxME0xNSAzMGgxNW0tNy41LTE0LjV2NU0yMCAxOGg1IiBzdHJva2UtbGluZWpvaW49Im1pdGVyIi8+PC9nPjwvc3ZnPg==');
+}
+piece.knight.white {
+  background-image: url('data:image/svg+xml;base64,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');
+}
+piece.rook.white {
+  background-image: url('data:image/svg+xml;base64,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');
+}
+piece.queen.white {
+  background-image: url('data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHdpZHRoPSI0NSIgaGVpZ2h0PSI0NSI+PGcgZmlsbD0iI2ZmZiIgZmlsbC1ydWxlPSJldmVub2RkIiBzdHJva2U9IiMwMDAiIHN0cm9rZS13aWR0aD0iMS41IiBzdHJva2UtbGluZWNhcD0icm91bmQiIHN0cm9rZS1saW5lam9pbj0icm91bmQiPjxwYXRoIGQ9Ik04IDEyYTIgMiAwIDEgMS00IDAgMiAyIDAgMSAxIDQgMHptMTYuNS00LjVhMiAyIDAgMSAxLTQgMCAyIDIgMCAxIDEgNCAwek00MSAxMmEyIDIgMCAxIDEtNCAwIDIgMiAwIDEgMSA0IDB6TTE2IDguNWEyIDIgMCAxIDEtNCAwIDIgMiAwIDEgMSA0IDB6TTMzIDlhMiAyIDAgMSAxLTQgMCAyIDIgMCAxIDEgNCAweiIvPjxwYXRoIGQ9Ik05IDI2YzguNS0xLjUgMjEtMS41IDI3IDBsMi0xMi03IDExVjExbC01LjUgMTMuNS0zLTE1LTMgMTUtNS41LTE0VjI1TDcgMTRsMiAxMnoiIHN0cm9rZS1saW5lY2FwPSJidXR0Ii8+PHBhdGggZD0iTTkgMjZjMCAyIDEuNSAyIDIuNSA0IDEgMS41IDEgMSAuNSAzLjUtMS41IDEtMS41IDIuNS0xLjUgMi41LTEuNSAxLjUuNSAyLjUuNSAyLjUgNi41IDEgMTYuNSAxIDIzIDAgMCAwIDEuNS0xIDAtMi41IDAgMCAuNS0xLjUtMS0yLjUtLjUtMi41LS41LTIgLjUtMy41IDEtMiAyLjUtMiAyLjUtNC04LjUtMS41LTE4LjUtMS41LTI3IDB6IiBzdHJva2UtbGluZWNhcD0iYnV0dCIvPjxwYXRoIGQ9Ik0xMS41IDMwYzMuNS0xIDE4LjUtMSAyMiAwTTEyIDMzLjVjNi0xIDE1LTEgMjEgMCIgZmlsbD0ibm9uZSIvPjwvZz48L3N2Zz4=');
+}
+piece.king.white {
+  background-image: url('data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHdpZHRoPSI0NSIgaGVpZ2h0PSI0NSI+PGcgZmlsbD0ibm9uZSIgZmlsbC1ydWxlPSJldmVub2RkIiBzdHJva2U9IiMwMDAiIHN0cm9rZS13aWR0aD0iMS41IiBzdHJva2UtbGluZWNhcD0icm91bmQiIHN0cm9rZS1saW5lam9pbj0icm91bmQiPjxwYXRoIGQ9Ik0yMi41IDExLjYzVjZNMjAgOGg1IiBzdHJva2UtbGluZWpvaW49Im1pdGVyIi8+PHBhdGggZD0iTTIyLjUgMjVzNC41LTcuNSAzLTEwLjVjMCAwLTEtMi41LTMtMi41cy0zIDIuNS0zIDIuNWMtMS41IDMgMyAxMC41IDMgMTAuNSIgZmlsbD0iI2ZmZiIgc3Ryb2tlLWxpbmVjYXA9ImJ1dHQiIHN0cm9rZS1saW5lam9pbj0ibWl0ZXIiLz48cGF0aCBkPSJNMTEuNSAzN2M1LjUgMy41IDE1LjUgMy41IDIxIDB2LTdzOS00LjUgNi0xMC41Yy00LTYuNS0xMy41LTMuNS0xNiA0VjI3di0zLjVjLTMuNS03LjUtMTMtMTAuNS0xNi00LTMgNiA1IDEwIDUgMTBWMzd6IiBmaWxsPSIjZmZmIi8+PHBhdGggZD0iTTExLjUgMzBjNS41LTMgMTUuNS0zIDIxIDBtLTIxIDMuNWM1LjUtMyAxNS41LTMgMjEgMG0tMjEgMy41YzUuNS0zIDE1LjUtMyAyMSAwIi8+PC9nPjwvc3ZnPg==');
+}
+piece.pawn.black {
+  background-image: url('data:image/svg+xml;base64,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');
+}
+piece.bishop.black {
+  background-image: url('data:image/svg+xml;base64,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');
+}
+piece.knight.black {
+  background-image: url('data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHdpZHRoPSI0NSIgaGVpZ2h0PSI0NSI+PGcgZmlsbD0ibm9uZSIgZmlsbC1ydWxlPSJldmVub2RkIiBzdHJva2U9IiMwMDAiIHN0cm9rZS13aWR0aD0iMS41IiBzdHJva2UtbGluZWNhcD0icm91bmQiIHN0cm9rZS1saW5lam9pbj0icm91bmQiPjxwYXRoIGQ9Ik0yMiAxMGMxMC41IDEgMTYuNSA4IDE2IDI5SDE1YzAtOSAxMC02LjUgOC0yMSIgZmlsbD0iIzAwMCIvPjxwYXRoIGQ9Ik0yNCAxOGMuMzggMi45MS01LjU1IDcuMzctOCA5LTMgMi0yLjgyIDQuMzQtNSA0LTEuMDQyLS45NCAxLjQxLTMuMDQgMC0zLTEgMCAuMTkgMS4yMy0xIDItMSAwLTQuMDAzIDEtNC00IDAtMiA2LTEyIDYtMTJzMS44OS0xLjkgMi0zLjVjLS43My0uOTk0LS41LTItLjUtMyAxLTEgMyAyLjUgMyAyLjVoMnMuNzgtMS45OTIgMi41LTNjMSAwIDEgMyAxIDMiIGZpbGw9IiMwMDAiLz48cGF0aCBkPSJNOS41IDI1LjVhLjUuNSAwIDEgMS0xIDAgLjUuNSAwIDEgMSAxIDB6bTUuNDMzLTkuNzVhLjUgMS41IDMwIDEgMS0uODY2LS41LjUgMS41IDMwIDEgMSAuODY2LjV6IiBmaWxsPSIjZWNlY2VjIiBzdHJva2U9IiNlY2VjZWMiLz48cGF0aCBkPSJNMjQuNTUgMTAuNGwtLjQ1IDEuNDUuNS4xNWMzLjE1IDEgNS42NSAyLjQ5IDcuOSA2Ljc1UzM1Ljc1IDI5LjA2IDM1LjI1IDM5bC0uMDUuNWgyLjI1bC4wNS0uNWMuNS0xMC4wNi0uODgtMTYuODUtMy4yNS0yMS4zNC0yLjM3LTQuNDktNS43OS02LjY0LTkuMTktNy4xNmwtLjUxLS4xeiIgZmlsbD0iI2VjZWNlYyIgc3Ryb2tlPSJub25lIi8+PC9nPjwvc3ZnPg==');
+}
+piece.rook.black {
+  background-image: url('data:image/svg+xml;base64,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');
+}
+piece.queen.black {
+  background-image: url('data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHdpZHRoPSI0NSIgaGVpZ2h0PSI0NSI+PGcgZmlsbC1ydWxlPSJldmVub2RkIiBzdHJva2U9IiMwMDAiIHN0cm9rZS13aWR0aD0iMS41IiBzdHJva2UtbGluZWNhcD0icm91bmQiIHN0cm9rZS1saW5lam9pbj0icm91bmQiPjxnIHN0cm9rZT0ibm9uZSI+PGNpcmNsZSBjeD0iNiIgY3k9IjEyIiByPSIyLjc1Ii8+PGNpcmNsZSBjeD0iMTQiIGN5PSI5IiByPSIyLjc1Ii8+PGNpcmNsZSBjeD0iMjIuNSIgY3k9IjgiIHI9IjIuNzUiLz48Y2lyY2xlIGN4PSIzMSIgY3k9IjkiIHI9IjIuNzUiLz48Y2lyY2xlIGN4PSIzOSIgY3k9IjEyIiByPSIyLjc1Ii8+PC9nPjxwYXRoIGQ9Ik05IDI2YzguNS0xLjUgMjEtMS41IDI3IDBsMi41LTEyLjVMMzEgMjVsLS4zLTE0LjEtNS4yIDEzLjYtMy0xNC41LTMgMTQuNS01LjItMTMuNkwxNCAyNSA2LjUgMTMuNSA5IDI2eiIgc3Ryb2tlLWxpbmVjYXA9ImJ1dHQiLz48cGF0aCBkPSJNOSAyNmMwIDIgMS41IDIgMi41IDQgMSAxLjUgMSAxIC41IDMuNS0xLjUgMS0xLjUgMi41LTEuNSAyLjUtMS41IDEuNS41IDIuNS41IDIuNSA2LjUgMSAxNi41IDEgMjMgMCAwIDAgMS41LTEgMC0yLjUgMCAwIC41LTEuNS0xLTIuNS0uNS0yLjUtLjUtMiAuNS0zLjUgMS0yIDIuNS0yIDIuNS00LTguNS0xLjUtMTguNS0xLjUtMjcgMHoiIHN0cm9rZS1saW5lY2FwPSJidXR0Ii8+PHBhdGggZD0iTTExIDM4LjVhMzUgMzUgMSAwIDAgMjMgMCIgZmlsbD0ibm9uZSIgc3Ryb2tlLWxpbmVjYXA9ImJ1dHQiLz48cGF0aCBkPSJNMTEgMjlhMzUgMzUgMSAwIDEgMjMgMG0tMjEuNSAyLjVoMjBtLTIxIDNhMzUgMzUgMSAwIDAgMjIgMG0tMjMgM2EzNSAzNSAxIDAgMCAyNCAwIiBmaWxsPSJub25lIiBzdHJva2U9IiNlY2VjZWMiLz48L2c+PC9zdmc+');
+}
+piece.king.black {
+  background-image: url('data:image/svg+xml;base64,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');
+}
diff --git a/base_rules.js b/base_rules.js
new file mode 100644
index 0000000..ffb9fd6
--- /dev/null
+++ b/base_rules.js
@@ -0,0 +1,2083 @@
+import { Random } from "/utils/alea.js";
+import { ArrayFun } from "/utils/array.js";
+import PiPo from "/utils/PiPo.js";
+import Move from "/utils/Move.js";
+
+// NOTE: x coords: top to bottom (white perspective); y: left to right
+export default class ChessRules {
+
+  /////////////////////////
+  // VARIANT SPECIFICATIONS
+
+  // Some variants have specific options, like the number of pawns in Monster,
+  // or the board size for Pandemonium.
+  // Users can generally select a randomness level from 0 to 2.
+  static get Options() {
+    return {
+      // NOTE: some options are required for FEN generation, some aren't.
+      select: [{
+        label: "Randomness",
+        variable: "randomness",
+        defaut: 0,
+        options: [
+          { label: "Deterministic", value: 0 },
+          { label: "Symmetric random", value: 1 },
+          { label: "Asymmetric random", value: 2 }
+        ]
+      }],
+      check: [{
+        label: "Capture king?",
+        defaut: false,
+        variable: "taking"
+      }],
+      // Game modifiers (using "elementary variants"). Default: false
+      styles: [
+        "atomic",
+        "balance", //takes precedence over doublemove & progressive
+        "cannibal",
+        "capture",
+        "crazyhouse",
+        "cylinder", //ok with all
+        "dark",
+        "doublemove",
+        "madrasi",
+        "progressive", //(natural) priority over doublemove
+        "recycle",
+        "rifle",
+        "teleport",
+        "zen"
+      ]
+    };
+  }
+
+  // Pawns specifications
+  get pawnSpecs() {
+    return {
+      directions: { 'w': -1, 'b': 1 },
+      initShift: { w: 1, b: 1 },
+      twoSquares: true,
+      threeSquares: false,
+      canCapture: true,
+      captureBackward: false,
+      bidirectional: false,
+      promotions: ['r', 'n', 'b', 'q']
+    };
+  }
+
+  // Some variants don't have flags:
+  get hasFlags() {
+    return true;
+  }
+  // Or castle
+  get hasCastle() {
+    return this.hasFlags;
+  }
+
+  // En-passant captures allowed?
+  get hasEnpassant() {
+    return true;
+  }
+
+  get hasReserve() {
+    return (
+      !!this.options["crazyhouse"] ||
+      (!!this.options["recycle"] && !this.options["teleport"])
+    );
+  }
+
+  get noAnimate() {
+    return !!this.options["dark"];
+  }
+
+  // Some variants use click infos:
+  doClick([x, y]) {
+    if (typeof x != "number") return null; //click on reserves
+    if (
+      this.options["teleport"] && this.subTurn == 2 &&
+      this.board[x][y] == ""
+    ) {
+      return new Move({
+        start: {x: this.captured.x, y: this.captured.y},
+        appear: [
+          new PiPo({
+            x: x,
+            y: y,
+            c: this.captured.c, //this.turn,
+            p: this.captured.p
+          })
+        ],
+        vanish: []
+      });
+    }
+    return null;
+  }
+
+  ////////////////////
+  // COORDINATES UTILS
+
+  // 3 --> d (column number to letter)
+  static CoordToColumn(colnum) {
+    return String.fromCharCode(97 + colnum);
+  }
+
+  // d --> 3 (column letter to number)
+  static ColumnToCoord(columnStr) {
+    return columnStr.charCodeAt(0) - 97;
+  }
+
+  // 7 (numeric) --> 1 (str) [from black viewpoint].
+  static CoordToRow(rownum) {
+    return rownum;
+  }
+
+  // NOTE: wrong row index (1 should be 7 ...etc). But OK for the usage.
+  static RowToCoord(rownumStr) {
+    // NOTE: 30 is way more than enough (allow up to 29 rows on one character)
+    return parseInt(rownumStr, 30);
+  }
+
+  // a2 --> {x:2,y:0} (this is in fact a6)
+  static SquareToCoords(sq) {
+    return {
+      x: ChessRules.RowToCoord(sq[1]),
+      // NOTE: column is always one char => max 26 columns
+      y: ChessRules.ColumnToCoord(sq[0])
+    };
+  }
+
+  // {x:0,y:4} --> e0 (should be e8)
+  static CoordsToSquare(coords) {
+    return (
+      ChessRules.CoordToColumn(coords.y) + ChessRules.CoordToRow(coords.x)
+    );
+  }
+
+  coordsToId([x, y]) {
+    if (typeof x == "number")
+      return `${this.containerId}|sq-${x.toString(30)}-${y.toString(30)}`;
+    // Reserve :
+    return `${this.containerId}|rsq-${x}-${y}`;
+  }
+
+  idToCoords(targetId) {
+    if (!targetId) return null; //outside page, maybe...
+    const idParts = targetId.split('|'); //prefix|sq-2-3 (start at 0 => 3,4)
+    if (
+      idParts.length < 2 ||
+      idParts[0] != this.containerId ||
+      !idParts[1].match(/sq-[0-9a-zA-Z]-[0-9a-zA-Z]/)
+    ) {
+      return null;
+    }
+    const squares = idParts[1].split('-');
+    if (squares[0] == "sq")
+      return [ parseInt(squares[1], 30), parseInt(squares[2], 30) ];
+    // squares[0] == "rsq" : reserve, 'c' + 'p' (letters)
+    return [squares[1], squares[2]];
+  }
+
+  /////////////
+  // FEN UTILS
+
+  // Turn "wb" into "B" (for FEN)
+  board2fen(b) {
+    return b[0] == "w" ? b[1].toUpperCase() : b[1];
+  }
+
+  // Turn "p" into "bp" (for board)
+  fen2board(f) {
+    return f.charCodeAt(0) <= 90 ? "w" + f.toLowerCase() : "b" + f;
+  }
+
+  // Setup the initial random-or-not (asymmetric-or-not) position
+  genRandInitFen(seed) {
+    Random.setSeed(seed);
+
+    let fen, flags = "0707";
+    if (this.options.randomness == 0 || !this.options.randomness)
+      // Deterministic:
+      fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w 0";
+
+    else {
+      // Randomize
+      let pieces = { w: new Array(8), b: new Array(8) };
+      flags = "";
+      // Shuffle pieces on first (and last rank if randomness == 2)
+      for (let c of ["w", "b"]) {
+        if (c == 'b' && this.options.randomness == 1) {
+          pieces['b'] = pieces['w'];
+          flags += flags;
+          break;
+        }
+
+        let positions = ArrayFun.range(8);
+
+        // Get random squares for bishops
+        let randIndex = 2 * Random.randInt(4);
+        const bishop1Pos = positions[randIndex];
+        // The second bishop must be on a square of different color
+        let randIndex_tmp = 2 * Random.randInt(4) + 1;
+        const bishop2Pos = positions[randIndex_tmp];
+        // Remove chosen squares
+        positions.splice(Math.max(randIndex, randIndex_tmp), 1);
+        positions.splice(Math.min(randIndex, randIndex_tmp), 1);
+
+        // Get random squares for knights
+        randIndex = Random.randInt(6);
+        const knight1Pos = positions[randIndex];
+        positions.splice(randIndex, 1);
+        randIndex = Random.randInt(5);
+        const knight2Pos = positions[randIndex];
+        positions.splice(randIndex, 1);
+
+        // Get random square for queen
+        randIndex = Random.randInt(4);
+        const queenPos = positions[randIndex];
+        positions.splice(randIndex, 1);
+
+        // Rooks and king positions are now fixed,
+        // because of the ordering rook-king-rook
+        const rook1Pos = positions[0];
+        const kingPos = positions[1];
+        const rook2Pos = positions[2];
+
+        // Finally put the shuffled pieces in the board array
+        pieces[c][rook1Pos] = "r";
+        pieces[c][knight1Pos] = "n";
+        pieces[c][bishop1Pos] = "b";
+        pieces[c][queenPos] = "q";
+        pieces[c][kingPos] = "k";
+        pieces[c][bishop2Pos] = "b";
+        pieces[c][knight2Pos] = "n";
+        pieces[c][rook2Pos] = "r";
+        flags += rook1Pos.toString() + rook2Pos.toString();
+      }
+      fen = (
+        pieces["b"].join("") +
+        "/pppppppp/8/8/8/8/PPPPPPPP/" +
+        pieces["w"].join("").toUpperCase() +
+        " w 0"
+      );
+    }
+    // Add turn + flags + enpassant (+ reserve)
+    let parts = [];
+    if (this.hasFlags) parts.push(`"flags":"${flags}"`);
+    if (this.hasEnpassant) parts.push('"enpassant":"-"');
+    if (this.hasReserve) parts.push('"reserve":"000000000000"');
+    if (this.options["crazyhouse"]) parts.push('"ispawn":"-"');
+    if (parts.length >= 1) fen += " {" + parts.join(",") + "}";
+    return fen;
+  }
+
+  // "Parse" FEN: just return untransformed string data
+  parseFen(fen) {
+    const fenParts = fen.split(" ");
+    let res = {
+      position: fenParts[0],
+      turn: fenParts[1],
+      movesCount: fenParts[2]
+    };
+    if (fenParts.length > 3) res = Object.assign(res, JSON.parse(fenParts[3]));
+    return res;
+  }
+
+  // Return current fen (game state)
+  getFen() {
+    let fen = (
+      this.getBaseFen() + " " +
+      this.getTurnFen() + " " +
+      this.movesCount
+    );
+    let parts = [];
+    if (this.hasFlags) parts.push(`"flags":"${this.getFlagsFen()}"`);
+    if (this.hasEnpassant)
+      parts.push(`"enpassant":"${this.getEnpassantFen()}"`);
+    if (this.hasReserve) parts.push(`"reserve":"${this.getReserveFen()}"`);
+    if (this.options["crazyhouse"])
+      parts.push(`"ispawn":"${this.getIspawnFen()}"`);
+    if (parts.length >= 1) fen += " {" + parts.join(",") + "}";
+    return fen;
+  }
+
+  // Position part of the FEN string
+  getBaseFen() {
+    const format = (count) => {
+      // if more than 9 consecutive free spaces, break the integer,
+      // otherwise FEN parsing will fail.
+      if (count <= 9) return count;
+      // Most boards of size < 18:
+      if (count <= 18) return "9" + (count - 9);
+      // Except Gomoku:
+      return "99" + (count - 18);
+    };
+    let position = "";
+    for (let i = 0; i < this.size.y; i++) {
+      let emptyCount = 0;
+      for (let j = 0; j < this.size.x; j++) {
+        if (this.board[i][j] == "") emptyCount++;
+        else {
+          if (emptyCount > 0) {
+            // Add empty squares in-between
+            position += format(emptyCount);
+            emptyCount = 0;
+          }
+          position += this.board2fen(this.board[i][j]);
+        }
+      }
+      if (emptyCount > 0)
+        // "Flush remainder"
+        position += format(emptyCount);
+      if (i < this.size.y - 1) position += "/"; //separate rows
+    }
+    return position;
+  }
+
+  getTurnFen() {
+    return this.turn;
+  }
+
+  // Flags part of the FEN string
+  getFlagsFen() {
+    return ["w", "b"].map(c => {
+      return this.castleFlags[c].map(x => x.toString(30)).join("");
+    }).join("");
+  }
+
+  // Enpassant part of the FEN string
+  getEnpassantFen() {
+    if (!this.epSquare) return "-"; //no en-passant
+    return ChessRules.CoordsToSquare(this.epSquare);
+  }
+
+  getReserveFen() {
+    return (
+      ["w","b"].map(c => Object.values(this.reserve[c]).join("")).join("")
+    );
+  }
+
+  getIspawnFen() {
+    const coords = Object.keys(this.ispawn);
+    if (coords.length == 0) return "-";
+    return coords.map(ChessRules.CoordsToSquare).join(",");
+  }
+
+  // Set flags from fen (castle: white a,h then black a,h)
+  setFlags(fenflags) {
+    this.castleFlags = {
+      w: [0, 1].map(i => parseInt(fenflags.charAt(i), 30)),
+      b: [2, 3].map(i => parseInt(fenflags.charAt(i), 30))
+    };
+  }
+
+  //////////////////
+  // INITIALIZATION
+
+  // Fen string fully describes the game state
+  constructor(o) {
+    this.options = o.options;
+    this.playerColor = o.color;
+    this.afterPlay = o.afterPlay;
+
+    // FEN-related:
+    if (!o.fen) o.fen = this.genRandInitFen(o.seed);
+    const fenParsed = this.parseFen(o.fen);
+    this.board = this.getBoard(fenParsed.position);
+    this.turn = fenParsed.turn;
+    this.movesCount = parseInt(fenParsed.movesCount, 10);
+    this.setOtherVariables(fenParsed);
+
+    // Graphical (can use variables defined above)
+    this.containerId = o.element;
+    this.graphicalInit();
+  }
+
+  // Turn position fen into double array ["wb","wp","bk",...]
+  getBoard(position) {
+    const rows = position.split("/");
+    let board = ArrayFun.init(this.size.x, this.size.y, "");
+    for (let i = 0; i < rows.length; i++) {
+      let j = 0;
+      for (let indexInRow = 0; indexInRow < rows[i].length; indexInRow++) {
+        const character = rows[i][indexInRow];
+        const num = parseInt(character, 10);
+        // If num is a number, just shift j:
+        if (!isNaN(num)) j += num;
+        // Else: something at position i,j
+        else board[i][j++] = this.fen2board(character);
+      }
+    }
+    return board;
+  }
+
+  // Some additional variables from FEN (variant dependant)
+  setOtherVariables(fenParsed) {
+    // Set flags and enpassant:
+    if (this.hasFlags) this.setFlags(fenParsed.flags);
+    if (this.hasEnpassant)
+      this.epSquare = this.getEpSquare(fenParsed.enpassant);
+    if (this.hasReserve) this.initReserves(fenParsed.reserve);
+    if (this.options["crazyhouse"]) this.initIspawn(fenParsed.ispawn);
+    this.subTurn = 1; //may be unused
+    if (this.options["teleport"]) this.captured = null;
+    if (this.options["dark"]) {
+      this.enlightened = ArrayFun.init(this.size.x, this.size.y);
+      // Setup enlightened: squares reachable by player side
+      this.updateEnlightened(false);
+    }
+  }
+
+  updateEnlightened(withGraphics) {
+    let newEnlightened = ArrayFun.init(this.size.x, this.size.y, false);
+    const pawnShift = { w: -1, b: 1 };
+    // Add pieces positions + all squares reachable by moves (includes Zen):
+    // (watch out special pawns case)
+    for (let x=0; x<this.size.x; x++) {
+      for (let y=0; y<this.size.y; y++) {
+        if (this.board[x][y] != "" && this.getColor(x, y) == this.playerColor)
+        {
+          newEnlightened[x][y] = true;
+          const piece = this.getPiece(x, y);
+          if (piece == ChessRules.PAWN) {
+            // Attacking squares wouldn't be highlighted if no captures:
+            this.pieces(this.playerColor)[piece].attack.forEach(step => {
+              const [i, j] = [x + step[0], this.computeY(y + step[1])];
+              if (this.onBoard(i, j) && this.board[i][j] == "")
+                newEnlightened[i][j] = true;
+            });
+          }
+          this.getPotentialMovesFrom([x, y]).forEach(m => {
+            newEnlightened[m.end.x][m.end.y] = true;
+          });
+        }
+      }
+    }
+    if (this.epSquare) this.enlightEnpassant(newEnlightened);
+    if (withGraphics) this.graphUpdateEnlightened(newEnlightened);
+    this.enlightened = newEnlightened;
+  }
+
+  // Include en-passant capturing square if any:
+  enlightEnpassant(newEnlightened) {
+    const steps = this.pieces(this.playerColor)[ChessRules.PAWN].attack;
+    for (let step of steps) {
+      const x = this.epSquare.x - step[0],
+            y = this.computeY(this.epSquare.y - step[1]);
+      if (
+        this.onBoard(x, y) &&
+        this.getColor(x, y) == this.playerColor &&
+        this.getPiece(x, y) == ChessRules.PAWN
+      ) {
+        newEnlightened[x][this.epSquare.y] = true;
+        break;
+      }
+    }
+  }
+
+  // Apply diff this.enlightened --> newEnlightened on board
+  graphUpdateEnlightened(newEnlightened) {
+    let container = document.getElementById(this.containerId);
+    const r = container.getBoundingClientRect();
+    const pieceWidth = this.getPieceWidth(r.width);
+    for (let x=0; x<this.size.x; x++) {
+      for (let y=0; y<this.size.y; y++) {
+        if (this.enlightened[x][y] && !newEnlightened[x][y]) {
+          let elt = document.getElementById(this.coordsToId([x, y]));
+          elt.style.fillOpacity = "0.5";
+          if (this.g_pieces[x][y]) {
+            this.g_pieces[x][y].remove();
+            this.g_pieces[x][y] = null;
+          }
+        }
+        else if (!this.enlightened[x][y] && newEnlightened[x][y]) {
+          let elt = document.getElementById(this.coordsToId([x, y]));
+          elt.style.fillOpacity = "1";
+          if (this.board[x][y] != "") {
+            const piece = this.getPiece(x, y);
+            const color = this.getColor(x, y);
+            this.g_pieces[x][y] = document.createElement("piece");
+            let newClasses = [
+              this.pieces()[piece]["class"],
+              color == "w" ? "white" : "black"
+            ];
+            newClasses.forEach(cl => this.g_pieces[x][y].classList.add(cl));
+            this.g_pieces[x][y].style.width = pieceWidth + "px";
+            this.g_pieces[x][y].style.height = pieceWidth + "px";
+            const [ip, jp] = this.getPixelPosition(x, y, r);
+            this.g_pieces[x][y].style.transform =
+              `translate(${ip}px,${jp}px)`;
+            container.appendChild(this.g_pieces[x][y]);
+          }
+        }
+      }
+    }
+  }
+
+  // ordering p,r,n,b,q,k (most general + count in base 30 if needed)
+  initReserves(reserveStr) {
+    const counts = reserveStr.split("").map(c => parseInt(c, 30));
+    this.reserve = { w: {}, b: {} };
+    const pieceName = Object.keys(this.pieces());
+    for (let i of ArrayFun.range(12)) {
+      if (i < 6) this.reserve['w'][pieceName[i]] = counts[i];
+      else this.reserve['b'][pieceName[i-6]] = counts[i];
+    }
+  }
+
+  initIspawn(ispawnStr) {
+    if (ispawnStr != "-") {
+      this.ispawn = ispawnStr.split(",").map(ChessRules.SquareToCoords)
+                    .reduce((o, key) => ({ ...o, [key]: true}), {});
+    }
+    else this.ispawn = {};
+  }
+
+  getNbReservePieces(color) {
+    return (
+      Object.values(this.reserve[color]).reduce(
+        (oldV,newV) => oldV + (newV > 0 ? 1 : 0), 0)
+    );
+  }
+
+  //////////////
+  // VISUAL PART
+
+  getPieceWidth(rwidth) {
+    return (rwidth / this.size.y);
+  }
+
+  getSquareWidth(rwidth) {
+    return this.getPieceWidth(rwidth);
+  }
+
+  getReserveSquareSize(rwidth, nbR) {
+    const sqSize = this.getSquareWidth(rwidth);
+    return Math.min(sqSize, rwidth / nbR);
+  }
+
+  getReserveNumId(color, piece) {
+    return `${this.containerId}|rnum-${color}${piece}`;
+  }
+
+  graphicalInit() {
+    // NOTE: not window.onresize = this.re_drawBoardElts because scope (this)
+    window.onresize = () => this.re_drawBoardElements();
+    this.re_drawBoardElements();
+    this.initMouseEvents();
+    const container = document.getElementById(this.containerId);
+    new ResizeObserver(this.rescale).observe(container);
+  }
+
+  re_drawBoardElements() {
+    const board = this.getSvgChessboard();
+    const oppCol = ChessRules.GetOppCol(this.playerColor);
+    let container = document.getElementById(this.containerId);
+    container.innerHTML = "";
+    container.insertAdjacentHTML('beforeend', board);
+    let cb = container.querySelector("#" + this.containerId + "_SVG");
+    const aspectRatio = this.size.y / this.size.x;
+    // Compare window ratio width / height to aspectRatio:
+    const windowRatio = window.innerWidth / window.innerHeight;
+    let cbWidth, cbHeight;
+    if (windowRatio <= aspectRatio) {
+      // Limiting dimension is width:
+      cbWidth = Math.min(window.innerWidth, 767);
+      cbHeight = cbWidth / aspectRatio;
+    }
+    else {
+      // Limiting dimension is height:
+      cbHeight = Math.min(window.innerHeight, 767);
+      cbWidth = cbHeight * aspectRatio;
+    }
+    if (this.reserve) {
+      const sqSize = cbWidth / this.size.y;
+      // NOTE: allocate space for reserves (up/down) even if they are empty
+      if ((window.innerHeight - cbHeight) / 2 < sqSize + 5) {
+        cbHeight = window.innerHeight - 2 * (sqSize + 5);
+        cbWidth = cbHeight * aspectRatio;
+      }
+    }
+    container.style.width = cbWidth + "px";
+    container.style.height = cbHeight + "px";
+    // Center chessboard:
+    const spaceLeft = (window.innerWidth - cbWidth) / 2,
+          spaceTop = (window.innerHeight - cbHeight) / 2;
+    container.style.left = spaceLeft + "px";
+    container.style.top = spaceTop + "px";
+    // Give sizes instead of recomputing them,
+    // because chessboard might not be drawn yet.
+    this.setupPieces({
+      width: cbWidth,
+      height: cbHeight,
+      x: spaceLeft,
+      y: spaceTop
+    });
+  }
+
+  // Get SVG board (background, no pieces)
+  getSvgChessboard() {
+    const [sizeX, sizeY] = [this.size.x, this.size.y];
+    const flipped = (this.playerColor == 'b');
+    let board = `
+      <svg
+        viewBox="0 0 80 80"
+        version="1.1"
+        id="${this.containerId}_SVG">
+      <g>`;
+    for (let i=0; i < sizeX; i++) {
+      for (let j=0; j < sizeY; j++) {
+        const ii = (flipped ? this.size.x - 1 - i : i);
+        const jj = (flipped ? this.size.y - 1 - j : j);
+        let fillOpacity = '1';
+        if (this.options["dark"] && !this.enlightened[ii][jj])
+          fillOpacity = '0.5';
+        // NOTE: x / y reversed because coordinates system is reversed.
+        // TODO: CSS "wood" style, rect --> style --> background-image ?
+        board += `<rect style="fill-opacity:${fillOpacity};
+                               fill:#${this.getSquareColor(ii, jj)}"
+          id="${this.coordsToId([ii, jj])}"
+          width="10"
+          height="10"
+          x="${10*j}"
+          y="${10*i}" />`;
+      }
+    }
+    board += "</g></svg>";
+    return board;
+  }
+
+  // Generally light square bottom-right; TODO: user-defined colors at least
+  getSquareColor(i, j) {
+    return ((i+j) % 2 == 0 ? "f0d9b5": "b58863");
+  }
+
+  setupPieces(r) {
+    if (this.g_pieces) {
+      // Refreshing: delete old pieces first
+      for (let i=0; i<this.size.x; i++) {
+        for (let j=0; j<this.size.y; j++) {
+          if (this.g_pieces[i][j]) {
+            this.g_pieces[i][j].remove();
+            this.g_pieces[i][j] = null;
+          }
+        }
+      }
+    }
+    else this.g_pieces = ArrayFun.init(this.size.x, this.size.y, null);
+    let container = document.getElementById(this.containerId);
+    const pieceWidth = this.getPieceWidth(r.width);
+    for (let i=0; i < this.size.x; i++) {
+      for (let j=0; j < this.size.y; j++) {
+        if (
+          this.board[i][j] != "" &&
+          (!this.options["dark"] || this.enlightened[i][j])
+        ) {
+          const piece = this.getPiece(i, j);
+          const color = this.getColor(i, j);
+          this.g_pieces[i][j] = document.createElement("piece");
+          this.g_pieces[i][j].classList.add(this.pieces()[piece]["class"]);
+          this.g_pieces[i][j].classList.add(color == "w" ? "white" : "black");
+          this.g_pieces[i][j].style.width = pieceWidth + "px";
+          this.g_pieces[i][j].style.height = pieceWidth + "px";
+          const [ip, jp] = this.getPixelPosition(i, j, r);
+          this.g_pieces[i][j].style.transform = `translate(${ip}px,${jp}px)`;
+          container.appendChild(this.g_pieces[i][j]);
+        }
+      }
+    }
+    if (this.reserve) this.re_drawReserve(['w', 'b'], r);
+  }
+
+  // NOTE: assume !!this.reserve
+  re_drawReserve(colors, r) {
+    if (this.r_pieces) {
+      // Remove (old) reserve pieces
+      for (let c of colors) {
+        if (!this.reserve[c]) continue;
+        Object.keys(this.reserve[c]).forEach(p => {
+          if (this.r_pieces[c][p]) {
+            this.r_pieces[c][p].remove();
+            delete this.r_pieces[c][p];
+            const numId = this.getReserveNumId(c, p);
+            document.getElementById(numId).remove();
+          }
+        });
+        let reservesDiv = document.getElementById("reserves_" + c);
+        if (reservesDiv) reservesDiv.remove();
+      }
+    }
+    else this.r_pieces = { 'w': {}, 'b': {} };
+    if (!r) {
+      const container = document.getElementById(this.containerId);
+      r = container.getBoundingClientRect();
+    }
+    const epsilon = 1e-4; //fix display bug on Firefox at least
+    for (let c of colors) {
+      if (!this.reserve[c]) continue;
+      const nbR = this.getNbReservePieces(c);
+      if (nbR == 0) continue;
+      const sqResSize = this.getReserveSquareSize(r.width, nbR);
+      let ridx = 0;
+      const vShift = (c == this.playerColor ? r.height + 5 : -sqResSize - 5);
+      const [i0, j0] = [r.x, r.y + vShift];
+      let rcontainer = document.createElement("div");
+      rcontainer.id = "reserves_" + c;
+      rcontainer.classList.add("reserves");
+      rcontainer.style.left = i0 + "px";
+      rcontainer.style.top = j0 + "px";
+      rcontainer.style.width = (nbR * sqResSize) + "px";
+      rcontainer.style.height = sqResSize + "px";
+      document.getElementById("boardContainer").appendChild(rcontainer);
+      for (let p of Object.keys(this.reserve[c])) {
+        if (this.reserve[c][p] == 0) continue;
+        let r_cell = document.createElement("div");
+        r_cell.id = this.coordsToId([c, p]);
+        r_cell.classList.add("reserve-cell");
+        r_cell.style.width = (sqResSize - epsilon) + "px";
+        r_cell.style.height = (sqResSize - epsilon) + "px";
+        rcontainer.appendChild(r_cell);
+        let piece = document.createElement("piece");
+        const pieceSpec = this.pieces(c)[p];
+        piece.classList.add(pieceSpec["class"]);
+        piece.classList.add(c == 'w' ? "white" : "black");
+        piece.style.width = "100%";
+        piece.style.height = "100%";
+        this.r_pieces[c][p] = piece;
+        r_cell.appendChild(piece);
+        let number = document.createElement("div");
+        number.textContent = this.reserve[c][p];
+        number.classList.add("reserve-num");
+        number.id = this.getReserveNumId(c, p);
+        const fontSize = "1.3em";
+        number.style.fontSize = fontSize;
+        number.style.fontSize = fontSize;
+        r_cell.appendChild(number);
+        ridx++;
+      }
+    }
+  }
+
+  updateReserve(color, piece, count) {
+    const oldCount = this.reserve[color][piece];
+    this.reserve[color][piece] = count;
+    // Redrawing is much easier if count==0
+    if ([oldCount, count].includes(0)) this.re_drawReserve([color]);
+    else {
+      const numId = this.getReserveNumId(color, piece);
+      document.getElementById(numId).textContent = count;
+    }
+  }
+
+  // After resize event: no need to destroy/recreate pieces
+  rescale() {
+    let container = document.getElementById(this.containerId);
+    if (!container) return; //useful at initial loading
+    const r = container.getBoundingClientRect();
+    const newRatio = r.width / r.height;
+    const aspectRatio = this.size.y / this.size.x;
+    let newWidth = r.width,
+        newHeight = r.height;
+    if (newRatio > aspectRatio) {
+      newWidth = r.height * aspectRatio;
+      container.style.width = newWidth + "px";
+    }
+    else if (newRatio < aspectRatio) {
+      newHeight = r.width / aspectRatio;
+      container.style.height = newHeight + "px";
+    }
+    const newX = (window.innerWidth - newWidth) / 2;
+    container.style.left = newX + "px";
+    const newY = (window.innerHeight - newHeight) / 2;
+    container.style.top = newY + "px";
+    const newR = { x: newX, y: newY, width: newWidth, height: newHeight };
+    const pieceWidth = this.getPieceWidth(newWidth);
+    for (let i=0; i < this.size.x; i++) {
+      for (let j=0; j < this.size.y; j++) {
+        if (this.board[i][j] != "") {
+          // NOTE: could also use CSS transform "scale"
+          this.g_pieces[i][j].style.width = pieceWidth + "px";
+          this.g_pieces[i][j].style.height = pieceWidth + "px";
+          const [ip, jp] = this.getPixelPosition(i, j, newR);
+          this.g_pieces[i][j].style.transform = `translate(${ip}px,${jp}px)`;
+        }
+      }
+    }
+    if (this.reserve) this.rescaleReserve(newR);
+  }
+
+  rescaleReserve(r) {
+    const epsilon = 1e-4;
+    for (let c of ['w','b']) {
+      if (!this.reserve[c]) continue;
+      const nbR = this.getNbReservePieces(c);
+      if (nbR == 0) continue;
+      // Resize container first
+      const sqResSize = this.getReserveSquareSize(r.width, nbR);
+      const vShift = (c == this.playerColor ? r.height + 5 : -sqResSize - 5);
+      const [i0, j0] = [r.x, r.y + vShift];
+      let rcontainer = document.getElementById("reserves_" + c);
+      rcontainer.style.left = i0 + "px";
+      rcontainer.style.top = j0 + "px";
+      rcontainer.style.width = (nbR * sqResSize) + "px";
+      rcontainer.style.height = sqResSize + "px";
+      // And then reserve cells:
+      const rpieceWidth = this.getReserveSquareSize(r.width, nbR);
+      Object.keys(this.reserve[c]).forEach(p => {
+        if (this.reserve[c][p] == 0) return;
+        let r_cell = document.getElementById(this.coordsToId([c, p]));
+        r_cell.style.width = (sqResSize - epsilon) + "px";
+        r_cell.style.height = (sqResSize - epsilon) + "px";
+      });
+    }
+  }
+
+  // Return the absolute pixel coordinates given current position.
+  // Our coordinate system differs from CSS one (x <--> y).
+  // We return here the CSS coordinates (more useful).
+  getPixelPosition(i, j, r) {
+    const sqSize = this.getSquareWidth(r.width);
+    if (i < 0 || j < 0) return [0, 0]; //piece vanishes
+    const flipped = (this.playerColor == 'b');
+    const x = (flipped ? this.size.y - 1 - j : j) * sqSize;
+    const y = (flipped ? this.size.x - 1 - i : i) * sqSize;
+    return [x, y];
+  }
+
+  initMouseEvents() {
+    let container = document.getElementById(this.containerId);
+
+    const getOffset = e => {
+      if (e.clientX) return {x: e.clientX, y: e.clientY}; //Mouse
+      let touchLocation = null;
+      if (e.targetTouches && e.targetTouches.length >= 1)
+        // Touch screen, dragstart
+        touchLocation = e.targetTouches[0];
+      else if (e.changedTouches && e.changedTouches.length >= 1)
+        // Touch screen, dragend
+        touchLocation = e.changedTouches[0];
+      if (touchLocation)
+        return {x: touchLocation.pageX, y: touchLocation.pageY};
+      return [0, 0]; //Big trouble here =)
+    }
+
+    const centerOnCursor = (piece, e) => {
+      const centerShift = sqSize / 2;
+      const offset = getOffset(e);
+      piece.style.left = (offset.x - centerShift) + "px";
+      piece.style.top = (offset.y - centerShift) + "px";
+    }
+
+    let start = null,
+        r = null,
+        startPiece, curPiece = null,
+        sqSize;
+    const mousedown = (e) => {
+      r = container.getBoundingClientRect();
+      sqSize = this.getSquareWidth(r.width);
+      const square = this.idToCoords(e.target.id);
+      if (square) {
+        const [i, j] = square;
+        const move = this.doClick([i, j]);
+        if (move) this.playPlusVisual(move);
+        else {
+          if (typeof i != "number") startPiece = this.r_pieces[i][j];
+          else if (this.g_pieces[i][j]) startPiece = this.g_pieces[i][j];
+          if (startPiece && this.canIplay(i, j)) {
+            e.preventDefault();
+            start = { x: i, y: j };
+            curPiece = startPiece.cloneNode();
+            curPiece.style.transform = "none";
+            curPiece.style.zIndex = 5;
+            curPiece.style.width = sqSize + "px";
+            curPiece.style.height = sqSize + "px";
+            centerOnCursor(curPiece, e);
+            document.getElementById("boardContainer").appendChild(curPiece);
+            startPiece.style.opacity = "0.4";
+            container.style.cursor = "none";
+          }
+        }
+      }
+    };
+
+    const mousemove = (e) => {
+      if (start) {
+        e.preventDefault();
+        centerOnCursor(curPiece, e);
+      }
+    };
+
+    const mouseup = (e) => {
+      const newR = container.getBoundingClientRect();
+      if (newR.width != r.width || newR.height != r.height) {
+        this.rescale();
+        return;
+      }
+      if (!start) return;
+      const [x, y] = [start.x, start.y];
+      start = null;
+      e.preventDefault();
+      container.style.cursor = "pointer";
+      startPiece.style.opacity = "1";
+      const offset = getOffset(e);
+      const landingElt = document.elementFromPoint(offset.x, offset.y);
+      const sq = this.idToCoords(landingElt.id);
+      if (sq) {
+        const [i, j] = sq;
+        // NOTE: clearly suboptimal, but much easier, and not a big deal.
+        const potentialMoves = this.getPotentialMovesFrom([x, y])
+          .filter(m => m.end.x == i && m.end.y == j);
+        const moves = this.filterValid(potentialMoves);
+        if (moves.length >= 2) this.showChoices(moves, r);
+        else if (moves.length == 1) this.playPlusVisual(moves[0], r);
+      }
+      curPiece.remove();
+    };
+
+    if ('onmousedown' in window) {
+      document.addEventListener("mousedown", mousedown);
+      document.addEventListener("mousemove", mousemove);
+      document.addEventListener("mouseup", mouseup);
+    }
+    if ('ontouchstart' in window) {
+      document.addEventListener("touchstart", mousedown);
+      document.addEventListener("touchmove", mousemove);
+      document.addEventListener("touchend", mouseup);
+    }
+  }
+
+  showChoices(moves, r) {
+    let container = document.getElementById(this.containerId);
+    let choices = document.createElement("div");
+    choices.id = "choices";
+    choices.style.width = r.width + "px";
+    choices.style.height = r.height + "px";
+    choices.style.left = r.x + "px";
+    choices.style.top = r.y + "px";
+    container.style.opacity = "0.5";
+    let boardContainer = document.getElementById("boardContainer");
+    boardContainer.appendChild(choices);
+    const squareWidth = this.getSquareWidth(r.width);
+    const firstUpLeft = (r.width - (moves.length * squareWidth)) / 2;
+    const firstUpTop = (r.height - squareWidth) / 2;
+    const color = moves[0].appear[0].c;
+    const callback = (m) => {
+      container.style.opacity = "1";
+      boardContainer.removeChild(choices);
+      this.playPlusVisual(m, r);
+    }
+    for (let i=0; i < moves.length; i++) {
+      let choice = document.createElement("div");
+      choice.classList.add("choice");
+      choice.style.width = squareWidth + "px";
+      choice.style.height = squareWidth + "px";
+      choice.style.left = (firstUpLeft + i * squareWidth) + "px";
+      choice.style.top = firstUpTop + "px";
+      choice.style.backgroundColor = "lightyellow";
+      choice.onclick = () => callback(moves[i]);
+      const piece = document.createElement("piece");
+      const pieceSpec = this.pieces(color)[moves[i].appear[0].p];
+      piece.classList.add(pieceSpec["class"]);
+      piece.classList.add(color == 'w' ? "white" : "black");
+      piece.style.width = "100%";
+      piece.style.height = "100%";
+      choice.appendChild(piece);
+      choices.appendChild(choice);
+    }
+  }
+
+  //////////////
+  // BASIC UTILS
+
+  get size() {
+    return { "x": 8, "y": 8 };
+  }
+
+  // Color of thing on square (i,j). 'undefined' if square is empty
+  getColor(i, j) {
+    return this.board[i][j].charAt(0);
+  }
+
+  // Piece type on square (i,j). 'undefined' if square is empty
+  getPiece(i, j) {
+    return this.board[i][j].charAt(1);
+  }
+
+  // Get opponent color
+  static GetOppCol(color) {
+    return (color == "w" ? "b" : "w");
+  }
+
+  // Can thing on square1 take thing on square2
+  canTake([x1, y1], [x2, y2]) {
+    return (
+      (
+        (this.options["recycle"] || this.options["teleport"]) &&
+        this.getPiece(x2, y2) != ChessRules.KING
+      ) ||
+      (this.getColor(x1, y1) !== this.getColor(x2, y2))
+    );
+  }
+
+  // Is (x,y) on the chessboard?
+  onBoard(x, y) {
+    return x >= 0 && x < this.size.x && y >= 0 && y < this.size.y;
+  }
+
+  // Used in interface: 'side' arg == player color
+  canIplay(x, y) {
+    return (
+      this.playerColor == this.turn &&
+      (
+        (typeof x == "number" && this.getColor(x, y) == this.turn) ||
+        (typeof x == "string" && x == this.turn) //reserve
+      )
+    );
+  }
+
+  ////////////////////////
+  // PIECES SPECIFICATIONS
+
+  pieces(color) {
+    const pawnShift = (color == "w" ? -1 : 1);
+    return {
+      'p': {
+        "class": "pawn",
+        steps: [[pawnShift, 0]],
+        range: 1,
+        attack: [[pawnShift, 1], [pawnShift, -1]]
+      },
+      // rook
+      'r': {
+        "class": "rook",
+        steps: [[0, 1], [0, -1], [1, 0], [-1, 0]]
+      },
+      // knight
+      'n': {
+        "class": "knight",
+        steps: [
+          [1, 2], [1, -2], [-1, 2], [-1, -2],
+          [2, 1], [-2, 1], [2, -1], [-2, -1]
+        ],
+        range: 1
+      },
+      // bishop
+      'b': {
+        "class": "bishop",
+        steps: [[1, 1], [1, -1], [-1, 1], [-1, -1]]
+      },
+      // queen
+      'q': {
+        "class": "queen",
+        steps: [
+          [0, 1], [0, -1], [1, 0], [-1, 0],
+          [1, 1], [1, -1], [-1, 1], [-1, -1]
+        ]
+      },
+      // king
+      'k': {
+        "class": "king",
+        steps: [
+          [0, 1], [0, -1], [1, 0], [-1, 0],
+          [1, 1], [1, -1], [-1, 1], [-1, -1]
+        ],
+        range: 1
+      }
+    };
+  }
+
+  // Some pieces codes (for a clearer code)
+  static get PAWN() {
+    return "p";
+  }
+  static get QUEEN() {
+    return "q";
+  }
+  static get KING() {
+    return "k";
+  }
+
+  ////////////////////
+  // MOVES GENERATION
+
+  // For Cylinder: get Y coordinate
+  computeY(y) {
+    if (!this.options["cylinder"]) return y;
+    let res = y % this.size.y;
+    if (res < 0) res += this.size.y;
+    return res;
+  }
+
+  // Stop at the first capture found
+  atLeastOneCapture(color) {
+    color = color || this.turn;
+    const oppCol = ChessRules.GetOppCol(color);
+    for (let i = 0; i < this.size.x; i++) {
+      for (let j = 0; j < this.size.y; j++) {
+        if (this.board[i][j] != "" && this.getColor(i, j) == color) {
+          const specs = this.pieces(color)[this.getPiece(i, j)];
+          const steps = specs.attack || specs.steps;
+          outerLoop: for (let step of steps) {
+            let [ii, jj] = [i + step[0], this.computeY(j + step[1])];
+            let stepCounter = 1;
+            while (this.onBoard(ii, jj) && this.board[ii][jj] == "") {
+              if (specs.range <= stepCounter++) continue outerLoop;
+              ii += step[0];
+              jj = this.computeY(jj + step[1]);
+            }
+            if (
+              this.onBoard(ii, jj) &&
+              this.getColor(ii, jj) == oppCol &&
+              this.filterValid(
+                [this.getBasicMove([i, j], [ii, jj])]
+              ).length >= 1
+            ) {
+              return true;
+            }
+          }
+        }
+      }
+    }
+    return false;
+  }
+
+  getDropMovesFrom([c, p]) {
+    // NOTE: by design, this.reserve[c][p] >= 1 on user click
+    // (but not necessarily otherwise)
+    if (!this.reserve[c][p] || this.reserve[c][p] == 0) return [];
+    let moves = [];
+    for (let i=0; i<this.size.x; i++) {
+      for (let j=0; j<this.size.y; j++) {
+        // TODO: rather simplify this "if" and add post-condition: more general
+        if (
+          this.board[i][j] == "" &&
+          (!this.options["dark"] || this.enlightened[i][j]) &&
+          (
+            p != ChessRules.PAWN ||
+            (c == 'w' && i < this.size.x - 1) ||
+            (c == 'b' && i > 0)
+          )
+        ) {
+          moves.push(
+            new Move({
+              start: {x: c, y: p},
+              end: {x: i, y: j},
+              appear: [new PiPo({x: i, y: j, c: c, p: p})],
+              vanish: []
+            })
+          );
+        }
+      }
+    }
+    return moves;
+  }
+
+  // All possible moves from selected square
+  getPotentialMovesFrom(sq) {
+    if (typeof sq[0] == "string") return this.getDropMovesFrom(sq);
+    if (this.options["madrasi"] && this.isImmobilized(sq)) return [];
+    const piece = this.getPiece(sq[0], sq[1]);
+    let moves;
+    if (piece == ChessRules.PAWN) moves = this.getPotentialPawnMoves(sq);
+    else moves = this.getPotentialMovesOf(piece, sq);
+    if (
+      piece == ChessRules.KING &&
+      this.hasCastle &&
+      this.castleFlags[color || this.turn].some(v => v < this.size.y)
+    ) {
+      Array.prototype.push.apply(moves, this.getCastleMoves(sq));
+    }
+    return this.postProcessPotentialMoves(moves);
+  }
+
+  postProcessPotentialMoves(moves) {
+    if (moves.length == 0) return [];
+    const color = this.getColor(moves[0].start.x, moves[0].start.y);
+    const oppCol = ChessRules.GetOppCol(color);
+
+    if (this.options["capture"] && this.atLeastOneCapture()) {
+      // Filter out non-capturing moves (not using m.vanish because of
+      // self captures of Recycle and Teleport).
+      moves = moves.filter(m => {
+        return (
+          this.board[m.end.x][m.end.y] != "" &&
+          this.getColor(m.end.x, m.end.y) == oppCol
+        );
+      });
+    }
+
+    if (this.options["atomic"]) {
+      moves.forEach(m => {
+        if (
+          this.board[m.end.x][m.end.y] != "" &&
+          this.getColor(m.end.x, m.end.y) == oppCol
+        ) {
+          // Explosion!
+          let steps = [
+            [-1, -1],
+            [-1, 0],
+            [-1, 1],
+            [0, -1],
+            [0, 1],
+            [1, -1],
+            [1, 0],
+            [1, 1]
+          ];
+          for (let step of steps) {
+            let x = m.end.x + step[0];
+            let y = this.computeY(m.end.y + step[1]);
+            if (
+              this.onBoard(x, y) &&
+              this.board[x][y] != "" &&
+              this.getPiece(x, y) != ChessRules.PAWN
+            ) {
+              m.vanish.push(
+                new PiPo({
+                  p: this.getPiece(x, y),
+                  c: this.getColor(x, y),
+                  x: x,
+                  y: y
+                })
+              );
+            }
+          }
+          if (!this.options["rifle"]) m.appear.pop(); //nothin appears
+        }
+      });
+    }
+    return moves;
+  }
+
+  // For Madrasi:
+  // (redefined in Baroque etc, where Madrasi condition doesn't make sense)
+  isImmobilized([x, y]) {
+    const color = this.getColor(x, y);
+    const oppCol = ChessRules.GetOppCol(color);
+    const piece = this.getPiece(x, y);
+    const stepSpec = this.pieces(color)[piece];
+    let [steps, range] = [stepSpec.attack || stepSpec.steps, stepSpec.range];
+    outerLoop: for (let step of steps) {
+      let [i, j] = [x + step[0], y + step[1]];
+      let stepCounter = 1;
+      while (this.onBoard(i, j) && this.board[i][j] == "") {
+        if (range <= stepCounter++) continue outerLoop;
+        i += step[0];
+        j = this.computeY(j + step[1]);
+      }
+      if (
+        this.onBoard(i, j) &&
+        this.getColor(i, j) == oppCol &&
+        this.getPiece(i, j) == piece
+      ) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  // Generic method to find possible moves of "sliding or jumping" pieces
+  getPotentialMovesOf(piece, [x, y]) {
+    const color = this.getColor(x, y);
+    const stepSpec = this.pieces(color)[piece];
+    let [steps, range] = [stepSpec.steps, stepSpec.range];
+    let moves = [];
+    let explored = {}; //for Cylinder mode
+    outerLoop: for (let step of steps) {
+      let [i, j] = [x + step[0], this.computeY(y + step[1])];
+      let stepCounter = 1;
+      while (
+        this.onBoard(i, j) &&
+        this.board[i][j] == "" &&
+        !explored[i + "." + j]
+      ) {
+        explored[i + "." + j] = true;
+        moves.push(this.getBasicMove([x, y], [i, j]));
+        if (range <= stepCounter++) continue outerLoop;
+        i += step[0];
+        j = this.computeY(j + step[1]);
+      }
+      if (
+        this.onBoard(i, j) &&
+        (
+          !this.options["zen"] ||
+          this.getPiece(i, j) == ChessRules.KING ||
+          this.getColor(i, j) == color //OK for Recycle and Teleport
+        ) &&
+        this.canTake([x, y], [i, j]) &&
+        !explored[i + "." + j]
+      ) {
+        explored[i + "." + j] = true;
+        moves.push(this.getBasicMove([x, y], [i, j]));
+      }
+    }
+    if (this.options["zen"])
+      Array.prototype.push.apply(moves, this.getZenCaptures(x, y));
+    return moves;
+  }
+
+  getZenCaptures(x, y) {
+    let moves = [];
+    // Find reverse captures (opponent takes)
+    const color = this.getColor(x, y);
+    const oppCol = ChessRules.GetOppCol(color);
+    const pieces = this.pieces(oppCol);
+    Object.keys(pieces).forEach(p => {
+      if (p == ChessRules.KING) return; //king isn't captured this way
+      const steps = pieces[p].attack || pieces[p].steps;
+      const range = pieces[p].range;
+      steps.forEach(s => {
+        // From x,y: revert step
+        let [i, j] = [x - s[0], this.computeY(y - s[1])];
+        let stepCounter = 1;
+        while (this.onBoard(i, j) && this.board[i][j] == "") {
+          if (range <= stepCounter++) return;
+          i -= s[0];
+          j = this.computeY(j - s[1]);
+        }
+        if (
+          this.onBoard(i, j) &&
+          this.getPiece(i, j) == p &&
+          this.getColor(i, j) == oppCol && //condition for Recycle & Teleport
+          this.canTake([i, j], [x, y])
+        ) {
+          if (this.getPiece(x, y) != ChessRules.PAWN)
+            moves.push(this.getBasicMove([x, y], [i, j]));
+          else this.addPawnMoves([x, y], [i, j], moves);
+        }
+      });
+    });
+    return moves;
+  }
+
+  // Build a regular move from its initial and destination squares.
+  // tr: transformation
+  getBasicMove([sx, sy], [ex, ey], tr) {
+    const initColor = this.getColor(sx, sy);
+    const initPiece = this.board[sx][sy].charAt(1);
+    const destColor = (this.board[ex][ey] != "" ? this.getColor(ex, ey) : "");
+    let mv = new Move({
+      appear: [],
+      vanish: [],
+      start: {x:sx, y:sy},
+      end: {x:ex, y:ey}
+    });
+    if (
+      !this.options["rifle"] ||
+      this.board[ex][ey] == "" ||
+      destColor == initColor //Recycle, Teleport
+    ) {
+      mv.appear = [
+        new PiPo({
+          x: ex,
+          y: ey,
+          c: !!tr ? tr.c : initColor,
+          p: !!tr ? tr.p : initPiece
+        })
+      ];
+      mv.vanish = [
+        new PiPo({
+          x: sx,
+          y: sy,
+          c: initColor,
+          p: initPiece
+        })
+      ];
+    }
+    if (this.board[ex][ey] != "") {
+      mv.vanish.push(
+        new PiPo({
+          x: ex,
+          y: ey,
+          c: this.getColor(ex, ey),
+          p: this.board[ex][ey].charAt(1)
+        })
+      );
+      if (this.options["rifle"])
+        // Rifle captures are tricky in combination with Atomic etc,
+        // so it's useful to mark the move :
+        mv.capture = true;
+      if (this.options["cannibal"] && destColor != initColor) {
+        const lastIdx = mv.vanish.length - 1;
+        if (mv.appear.length >= 1) mv.appear[0].p = mv.vanish[lastIdx].p;
+        else if (this.options["rifle"]) {
+          mv.appear.unshift(
+            new PiPo({
+              x: sx,
+              y: sy,
+              c: initColor,
+              p: mv.vanish[lastIdx].p
+            })
+          );
+          mv.vanish.unshift(
+            new PiPo({
+              x: sx,
+              y: sy,
+              c: initColor,
+              p: initPiece
+            })
+          );
+        }
+      }
+    }
+    return mv;
+  }
+
+  // En-passant square, if any
+  getEpSquare(moveOrSquare) {
+    if (typeof moveOrSquare === "string") {
+      const square = moveOrSquare;
+      if (square == "-") return undefined;
+      return ChessRules.SquareToCoords(square);
+    }
+    // Argument is a move:
+    const move = moveOrSquare;
+    const s = move.start,
+          e = move.end;
+    if (
+      s.y == e.y &&
+      Math.abs(s.x - e.x) == 2 &&
+      // Next conditions for variants like Atomic or Rifle, Recycle...
+      (move.appear.length > 0 && move.appear[0].p == ChessRules.PAWN) &&
+      (move.vanish.length > 0 && move.vanish[0].p == ChessRules.PAWN)
+    ) {
+      return {
+        x: (s.x + e.x) / 2,
+        y: s.y
+      };
+    }
+    return undefined; //default
+  }
+
+  // Special case of en-passant captures: treated separately
+  getEnpassantCaptures([x, y], shiftX) {
+    const color = this.getColor(x, y);
+    const oppCol = ChessRules.GetOppCol(color);
+    let enpassantMove = null;
+    if (
+      !!this.epSquare &&
+      this.epSquare.x == x + shiftX &&
+      Math.abs(this.computeY(this.epSquare.y - y)) == 1 &&
+      this.getColor(x, this.epSquare.y) == oppCol //Doublemove guard...
+    ) {
+      const [epx, epy] = [this.epSquare.x, this.epSquare.y];
+      this.board[epx][epy] = oppCol + "p";
+      enpassantMove = this.getBasicMove([x, y], [epx, epy]);
+      this.board[epx][epy] = "";
+      const lastIdx = enpassantMove.vanish.length - 1; //think Rifle
+      enpassantMove.vanish[lastIdx].x = x;
+    }
+    return !!enpassantMove ? [enpassantMove] : [];
+  }
+
+  // Consider all potential promotions:
+  addPawnMoves([x1, y1], [x2, y2], moves, promotions) {
+    let finalPieces = [ChessRules.PAWN];
+    const color = this.getColor(x1, y1);
+    const lastRank = (color == "w" ? 0 : this.size.x - 1);
+    if (x2 == lastRank && (!this.options["rifle"] || this.board[x2][y2] == ""))
+    {
+      // promotions arg: special override for Hiddenqueen variant
+      if (promotions) finalPieces = promotions;
+      else if (this.pawnSpecs.promotions)
+        finalPieces = this.pawnSpecs.promotions;
+    }
+    for (let piece of finalPieces) {
+      const tr = (piece != ChessRules.PAWN ? { c: color, p: piece } : null);
+      moves.push(this.getBasicMove([x1, y1], [x2, y2], tr));
+    }
+  }
+
+  // What are the pawn moves from square x,y ?
+  getPotentialPawnMoves([x, y], promotions) {
+    const color = this.getColor(x, y); //this.turn doesn't work for Dark mode
+    const [sizeX, sizeY] = [this.size.x, this.size.y];
+    const pawnShiftX = this.pawnSpecs.directions[color];
+    const firstRank = (color == "w" ? sizeX - 1 : 0);
+    const forward = (color == 'w' ? -1 : 1);
+
+    // Pawn movements in shiftX direction:
+    const getPawnMoves = (shiftX) => {
+      let moves = [];
+      // NOTE: next condition is generally true (no pawn on last rank)
+      if (x + shiftX >= 0 && x + shiftX < sizeX) {
+        if (this.board[x + shiftX][y] == "") {
+          // One square forward (or backward)
+          this.addPawnMoves([x, y], [x + shiftX, y], moves, promotions);
+          // Next condition because pawns on 1st rank can generally jump
+          if (
+            this.pawnSpecs.twoSquares &&
+            (
+              (
+                color == 'w' &&
+                x >= this.size.x - 1 - this.pawnSpecs.initShift['w']
+              )
+              ||
+              (color == 'b' && x <= this.pawnSpecs.initShift['b'])
+            )
+          ) {
+            if (
+              shiftX == forward &&
+              this.board[x + 2 * shiftX][y] == ""
+            ) {
+              // Two squares jump
+              moves.push(this.getBasicMove([x, y], [x + 2 * shiftX, y]));
+              if (
+                this.pawnSpecs.threeSquares &&
+                this.board[x + 3 * shiftX, y] == ""
+              ) {
+                // Three squares jump
+                moves.push(this.getBasicMove([x, y], [x + 3 * shiftX, y]));
+              }
+            }
+          }
+        }
+        // Captures
+        if (this.pawnSpecs.canCapture) {
+          for (let shiftY of [-1, 1]) {
+            const yCoord = this.computeY(y + shiftY);
+            if (yCoord >= 0 && yCoord < sizeY) {
+              if (
+                this.board[x + shiftX][yCoord] != "" &&
+                this.canTake([x, y], [x + shiftX, yCoord]) &&
+                (
+                  !this.options["zen"] ||
+                  this.getPiece(x + shiftX, yCoord) == ChessRules.KING
+                )
+              ) {
+                this.addPawnMoves(
+                  [x, y], [x + shiftX, yCoord],
+                  moves, promotions
+                );
+              }
+              if (
+                this.pawnSpecs.captureBackward && shiftX == forward &&
+                x - shiftX >= 0 && x - shiftX < this.size.x &&
+                this.board[x - shiftX][yCoord] != "" &&
+                this.canTake([x, y], [x - shiftX, yCoord]) &&
+                (
+                  !this.options["zen"] ||
+                  this.getPiece(x + shiftX, yCoord) == ChessRules.KING
+                )
+              ) {
+                this.addPawnMoves(
+                  [x, y], [x - shiftX, yCoord],
+                  moves, promotions
+                );
+              }
+            }
+          }
+        }
+      }
+      return moves;
+    }
+
+    let pMoves = getPawnMoves(pawnShiftX);
+    if (this.pawnSpecs.bidirectional)
+      pMoves = pMoves.concat(getPawnMoves(-pawnShiftX));
+
+    if (this.hasEnpassant) {
+      // NOTE: backward en-passant captures are not considered
+      // because no rules define them (for now).
+      Array.prototype.push.apply(
+        pMoves,
+        this.getEnpassantCaptures([x, y], pawnShiftX)
+      );
+    }
+
+    if (this.options["zen"])
+      Array.prototype.push.apply(pMoves, this.getZenCaptures(x, y));
+
+    return pMoves;
+  }
+
+  // "castleInCheck" arg to let some variants castle under check
+  getCastleMoves([x, y], finalSquares, castleInCheck, castleWith) {
+    const c = this.getColor(x, y);
+
+    // Castling ?
+    const oppCol = ChessRules.GetOppCol(c);
+    let moves = [];
+    // King, then rook:
+    finalSquares =
+      finalSquares || [ [2, 3], [this.size.y - 2, this.size.y - 3] ];
+    const castlingKing = this.board[x][y].charAt(1);
+    castlingCheck: for (
+      let castleSide = 0;
+      castleSide < 2;
+      castleSide++ //large, then small
+    ) {
+      if (this.castleFlags[c][castleSide] >= this.size.y) continue;
+      // If this code is reached, rook and king are on initial position
+
+      // NOTE: in some variants this is not a rook
+      const rookPos = this.castleFlags[c][castleSide];
+      const castlingPiece = this.board[x][rookPos].charAt(1);
+      if (
+        this.board[x][rookPos] == "" ||
+        this.getColor(x, rookPos) != c ||
+        (!!castleWith && !castleWith.includes(castlingPiece))
+      ) {
+        // Rook is not here, or changed color (see Benedict)
+        continue;
+      }
+      // Nothing on the path of the king ? (and no checks)
+      const finDist = finalSquares[castleSide][0] - y;
+      let step = finDist / Math.max(1, Math.abs(finDist));
+      let i = y;
+      do {
+        if (
+          (!castleInCheck && this.underCheck([x, i], oppCol)) ||
+          (
+            this.board[x][i] != "" &&
+            // NOTE: next check is enough, because of chessboard constraints
+            (this.getColor(x, i) != c || ![rookPos, y].includes(i))
+          )
+        ) {
+          continue castlingCheck;
+        }
+        i += step;
+      } while (i != finalSquares[castleSide][0]);
+      // Nothing on the path to the rook?
+      step = (castleSide == 0 ? -1 : 1);
+      for (i = y + step; i != rookPos; i += step) {
+        if (this.board[x][i] != "") continue castlingCheck;
+      }
+
+      // Nothing on final squares, except maybe king and castling rook?
+      for (i = 0; i < 2; i++) {
+        if (
+          finalSquares[castleSide][i] != rookPos &&
+          this.board[x][finalSquares[castleSide][i]] != "" &&
+          (
+            finalSquares[castleSide][i] != y ||
+            this.getColor(x, finalSquares[castleSide][i]) != c
+          )
+        ) {
+          continue castlingCheck;
+        }
+      }
+
+      // If this code is reached, castle is valid
+      moves.push(
+        new Move({
+          appear: [
+            new PiPo({
+              x: x,
+              y: finalSquares[castleSide][0],
+              p: castlingKing,
+              c: c
+            }),
+            new PiPo({
+              x: x,
+              y: finalSquares[castleSide][1],
+              p: castlingPiece,
+              c: c
+            })
+          ],
+          vanish: [
+            // King might be initially disguised (Titan...)
+            new PiPo({ x: x, y: y, p: castlingKing, c: c }),
+            new PiPo({ x: x, y: rookPos, p: castlingPiece, c: c })
+          ],
+          end:
+            Math.abs(y - rookPos) <= 2
+              ? { x: x, y: rookPos }
+              : { x: x, y: y + 2 * (castleSide == 0 ? -1 : 1) }
+        })
+      );
+    }
+
+    return moves;
+  }
+
+  ////////////////////
+  // MOVES VALIDATION
+
+  // Is (king at) given position under check by "color" ?
+  underCheck([x, y], color) {
+    if (this.taking || this.options["dark"]) return false;
+    color = color || ChessRules.GetOppCol(this.getColor(x, y));
+    const pieces = this.pieces(color);
+    return Object.keys(pieces).some(p => {
+      return this.isAttackedBy([x, y], p, color, pieces[p]);
+    });
+  }
+
+  isAttackedBy([x, y], piece, color, stepSpec) {
+    const steps = stepSpec.attack || stepSpec.steps;
+    const range = stepSpec.range;
+    let explored = {}; //for Cylinder mode
+    outerLoop: for (let step of steps) {
+      let rx = x - step[0],
+          ry = this.computeY(y - step[1]);
+      let stepCounter = 1;
+      while (
+        this.onBoard(rx, ry) &&
+        this.board[rx][ry] == "" &&
+        !explored[rx + "." + ry]
+      ) {
+        explored[rx + "." + ry] = true;
+        if (range <= stepCounter++) continue outerLoop;
+        rx -= step[0];
+        ry = this.computeY(ry - step[1]);
+      }
+      if (
+        this.onBoard(rx, ry) &&
+        this.board[rx][ry] != "" &&
+        this.getPiece(rx, ry) == piece &&
+        this.getColor(rx, ry) == color &&
+        (!this.options["madrasi"] || !this.isImmobilized([rx, ry]))
+      ) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  // Stop at first king found (TODO: multi-kings)
+  searchKingPos(color) {
+    for (let i=0; i < this.size.x; i++) {
+      for (let j=0; j < this.size.y; j++) {
+        if (this.board[i][j] == color + 'k') return [i, j];
+      }
+    }
+    return [-1, -1]; //king not found
+  }
+
+  filterValid(moves) {
+    if (moves.length == 0) return [];
+    const color = this.turn;
+    const oppCol = ChessRules.GetOppCol(color);
+    if (this.options["balance"] && [1, 3].includes(this.movesCount)) {
+      // Forbid moves either giving check or exploding opponent's king:
+      const oppKingPos = this.searchKingPos(oppCol);
+      moves = moves.filter(m => {
+        if (
+          m.vanish.some(v => v.c == oppCol && v.p == ChessRules.KING) &&
+          m.appear.every(a => a.c != oppCol || a.p != ChessRUles.KING)
+        )
+          return false;
+        this.playOnBoard(m);
+        const res = !this.underCheck(oppKingPos, color);
+        this.undoOnBoard(m);
+        return res;
+      });
+    }
+    if (this.taking || this.options["dark"]) return moves;
+    const kingPos = this.searchKingPos(color);
+    let filtered = {}; //avoid re-checking similar moves (promotions...)
+    return moves.filter(m => {
+      const key = m.start.x + m.start.y + '.' + m.end.x + m.end.y;
+      if (!filtered[key]) {
+        this.playOnBoard(m);
+        let square = kingPos,
+            res = true; //a priori valid
+        if (m.vanish.some(v => v.p == ChessRules.KING && v.c == color)) {
+          // Search king in appear array:
+          const newKingIdx =
+            m.appear.findIndex(a => a.p == ChessRules.KING && a.c == color);
+          if (newKingIdx >= 0)
+            square = [m.appear[newKingIdx].x, m.appear[newKingIdx].y];
+          else res = false;
+        }
+        res &&= !this.underCheck(square, oppCol);
+        this.undoOnBoard(m);
+        filtered[key] = res;
+        return res;
+      }
+      return filtered[key];
+    });
+  }
+
+  /////////////////
+  // MOVES PLAYING
+
+  // Aggregate flags into one object
+  aggregateFlags() {
+    return this.castleFlags;
+  }
+
+  // Reverse operation
+  disaggregateFlags(flags) {
+    this.castleFlags = flags;
+  }
+
+  // Apply a move on board
+  playOnBoard(move) {
+    for (let psq of move.vanish) this.board[psq.x][psq.y] = "";
+    for (let psq of move.appear) this.board[psq.x][psq.y] = psq.c + psq.p;
+  }
+  // Un-apply the played move
+  undoOnBoard(move) {
+    for (let psq of move.appear) this.board[psq.x][psq.y] = "";
+    for (let psq of move.vanish) this.board[psq.x][psq.y] = psq.c + psq.p;
+  }
+
+  updateCastleFlags(move) {
+    // Update castling flags if start or arrive from/at rook/king locations
+    move.appear.concat(move.vanish).forEach(psq => {
+      if (
+        this.board[psq.x][psq.y] != "" &&
+        this.getPiece(psq.x, psq.y) == ChessRules.KING
+      ) {
+        this.castleFlags[psq.c] = [this.size.y, this.size.y];
+      }
+      // NOTE: not "else if" because king can capture enemy rook...
+      let c = '';
+      if (psq.x == 0) c = 'b';
+      else if (psq.x == this.size.x - 1) c = 'w';
+      if (c != '') {
+        const fidx = this.castleFlags[c].findIndex(f => f == psq.y);
+        if (fidx >= 0) this.castleFlags[c][fidx] = this.size.y;
+      }
+    });
+  }
+
+  prePlay(move) {
+    if (
+      typeof move.start.x == "number" &&
+      (!this.options["teleport"] || this.subTurn == 1)
+    ) {
+      // OK, not a drop move
+      if (
+        this.hasCastle &&
+        // If flags already off, no need to re-check:
+        Object.keys(this.castleFlags).some(c => {
+          return this.castleFlags[c].some(val => val < this.size.y)})
+      ) {
+        this.updateCastleFlags(move);
+      }
+      const initSquare = ChessRules.CoordsToSquare(move.start);
+      if (
+        this.options["crazyhouse"] &&
+        (!this.options["rifle"] || !move.capture)
+      ) {
+        if (this.ispawn[initSquare]) {
+          delete this.ispawn[initSquare];
+          this.ispawn[ChessRules.CoordsToSquare(move.end)] = true;
+        }
+        else if (
+          move.vanish[0].p == ChessRules.PAWN &&
+          move.appear[0].p != ChessRules.PAWN
+        ) {
+          this.ispawn[ChessRules.CoordsToSquare(move.end)] = true;
+        }
+      }
+    }
+    const minSize = Math.min(move.appear.length, move.vanish.length);
+    if (this.hasReserve) {
+      const color = this.turn;
+      for (let i=minSize; i<move.appear.length; i++) {
+        // Something appears = dropped on board (some exceptions, Chakart...)
+        const piece = move.appear[i].p;
+        this.updateReserve(color, piece, this.reserve[color][piece] - 1);
+      }
+      for (let i=minSize; i<move.vanish.length; i++) {
+        // Something vanish: add to reserve except if recycle & opponent
+        const piece = move.vanish[i].p;
+        if (this.options["crazyhouse"] || move.vanish[i].c == color)
+          this.updateReserve(color, piece, this.reserve[color][piece] + 1);
+      }
+    }
+  }
+
+  play(move) {
+    this.prePlay(move);
+    if (this.hasEnpassant) this.epSquare = this.getEpSquare(move);
+    this.playOnBoard(move);
+    this.postPlay(move);
+  }
+
+  postPlay(move) {
+    const color = this.turn;
+    const oppCol = ChessRules.GetOppCol(color);
+    if (this.options["dark"]) this.updateEnlightened(true);
+    if (this.options["teleport"]) {
+      if (
+        this.subTurn == 1 &&
+        move.vanish.length > move.appear.length &&
+        move.vanish[move.vanish.length - 1].c == color
+      ) {
+        const v = move.vanish[move.vanish.length - 1];
+        this.captured = {x: v.x, y: v.y, c: v.c, p: v.p};
+        this.subTurn = 2;
+        return;
+      }
+      this.captured = null;
+    }
+    if (this.options["balance"]) {
+      if (![1, 3].includes(this.movesCount)) this.turn = oppCol;
+    }
+    else {
+      if (
+        (
+          this.options["doublemove"] &&
+          this.movesCount >= 1 &&
+          this.subTurn == 1
+        ) ||
+        (this.options["progressive"] && this.subTurn <= this.movesCount)
+      ) {
+        const oppKingPos = this.searchKingPos(oppCol);
+        if (oppKingPos[0] >= 0 && !this.underCheck(oppKingPos, color)) {
+          this.subTurn++;
+          return;
+        }
+      }
+      this.turn = oppCol;
+    }
+    this.movesCount++;
+    this.subTurn = 1;
+  }
+
+  // "Stop at the first move found"
+  atLeastOneMove(color) {
+    color = color || this.turn;
+    for (let i = 0; i < this.size.x; i++) {
+      for (let j = 0; j < this.size.y; j++) {
+        if (this.board[i][j] != "" && this.getColor(i, j) == color) {
+          // TODO?: do not search all possible moves here
+          const moves = this.getPotentialMovesFrom([i, j]);
+          if (moves.some(m => this.filterValid([m]).length >= 1)) return true;
+        }
+      }
+    }
+    if (this.hasReserve && this.reserve[color]) {
+      for (let p of Object.keys(this.reserve[color])) {
+        const moves = this.getDropMovesFrom([color, p]);
+        if (moves.some(m => this.filterValid([m]).length >= 1)) return true;
+      }
+    }
+    return false;
+  }
+
+  // What is the score ? (Interesting if game is over)
+  getCurrentScore(move) {
+    const color = this.turn;
+    const oppCol = ChessRules.GetOppCol(color);
+    const kingPos = [this.searchKingPos(color), this.searchKingPos(oppCol)];
+    if (kingPos[0][0] < 0 && kingPos[1][0] < 0) return "1/2";
+    if (kingPos[0][0] < 0) return (color == "w" ? "0-1" : "1-0");
+    if (kingPos[1][0] < 0) return (color == "w" ? "1-0" : "0-1");
+    if (this.atLeastOneMove()) return "*";
+    // No valid move: stalemate or checkmate?
+    if (!this.underCheck(kingPos, color)) return "1/2";
+    // OK, checkmate
+    return (color == "w" ? "0-1" : "1-0");
+  }
+
+  // NOTE: quite suboptimal for eg. Benedict (TODO?)
+  playVisual(move, r) {
+    move.vanish.forEach(v => {
+      if (!this.enlightened || this.enlightened[v.x][v.y]) {
+        this.g_pieces[v.x][v.y].remove();
+        this.g_pieces[v.x][v.y] = null;
+      }
+    });
+    let container = document.getElementById(this.containerId);
+    if (!r) r = container.getBoundingClientRect();
+    const pieceWidth = this.getPieceWidth(r.width);
+    move.appear.forEach(a => {
+      if (this.enlightened && !this.enlightened[a.x][a.y]) return;
+      this.g_pieces[a.x][a.y] = document.createElement("piece");
+      this.g_pieces[a.x][a.y].classList.add(this.pieces()[a.p]["class"]);
+      this.g_pieces[a.x][a.y].classList.add(a.c == "w" ? "white" : "black");
+      this.g_pieces[a.x][a.y].style.width = pieceWidth + "px";
+      this.g_pieces[a.x][a.y].style.height = pieceWidth + "px";
+      const [ip, jp] = this.getPixelPosition(a.x, a.y, r);
+      this.g_pieces[a.x][a.y].style.transform = `translate(${ip}px,${jp}px)`;
+      container.appendChild(this.g_pieces[a.x][a.y]);
+    });
+  }
+
+  playPlusVisual(move, r) {
+    this.playVisual(move, r);
+    this.play(move);
+    this.afterPlay(move); //user method
+  }
+
+  // Assumes reserve on top (usage case otherwise? TODO?)
+  getReserveShift(c, p, r) {
+    let nbR = 0,
+        ridx = 0;
+    for (let pi of Object.keys(this.reserve[c])) {
+      if (this.reserve[c][pi] == 0) continue;
+      if (pi == p) ridx = nbR;
+      nbR++;
+    }
+    const rsqSize = this.getReserveSquareSize(r.width, nbR);
+    return [ridx * rsqSize, rsqSize]; //slightly inaccurate... TODO?
+  }
+
+  animate(move, callback) {
+    if (this.noAnimate) {
+      callback();
+      return;
+    }
+    const [i1, j1] = [move.start.x, move.start.y];
+    const dropMove = (typeof i1 == "string");
+    const startArray = (dropMove ? this.r_pieces : this.g_pieces);
+    let startPiece = startArray[i1][j1];
+    let container = document.getElementById(this.containerId);
+    const clonePiece = (
+      !dropMove &&
+      this.options["rifle"] ||
+      (this.options["teleport"] && this.subTurn == 2)
+    );
+    if (clonePiece) {
+      startPiece = startPiece.cloneNode();
+      if (this.options["rifle"]) startArray[i1][j1].style.opacity = "0";
+      if (this.options["teleport"] && this.subTurn == 2) {
+        const pieces = this.pieces();
+        const startCode = (dropMove ? j1 : this.getPiece(i1, j1));
+        startPiece.classList.remove(pieces[startCode]["class"]);
+        startPiece.classList.add(pieces[this.captured.p]["class"]);
+        // Color: OK
+      }
+      container.appendChild(startPiece);
+    }
+    const [i2, j2] = [move.end.x, move.end.y];
+    let startCoords;
+    if (dropMove) {
+      startCoords = [
+        i1 == this.playerColor ? this.size.x : 0,
+        this.size.y / 2 //not trying to be accurate here... (TODO?)
+      ];
+    }
+    else startCoords = [i1, j1];
+    const r = container.getBoundingClientRect();
+    const arrival = this.getPixelPosition(i2, j2, r); //TODO: arrival on drop?
+    let rs = [0, 0];
+    if (dropMove) rs = this.getReserveShift(i1, j1, r);
+    const distance =
+      Math.sqrt((startCoords[0] - i2) ** 2 + (startCoords[1] - j2) ** 2);
+    const maxDist = Math.sqrt((this.size.x - 1)** 2 + (this.size.y - 1) ** 2);
+    const multFact = (distance - 1) / (maxDist - 1); //1 == minDist
+    const duration = 0.2 + multFact * 0.3;
+    startPiece.style.transform =
+      `translate(${arrival[0] + rs[0]}px, ${arrival[1] + rs[1]}px)`;
+    startPiece.style.transitionDuration = duration + "s";
+    setTimeout(
+      () => {
+        if (clonePiece) {
+          if (this.options["rifle"]) startArray[i1][j1].style.opacity = "1";
+          startPiece.remove();
+        }
+        callback();
+      },
+      duration * 1000
+    );
+  }
+
+  playReceivedMove(moves, callback) {
+    const r =
+      document.getElementById(this.containerId).getBoundingClientRect();
+    const animateRec = i => {
+      this.animate(moves[i], () => {
+        this.playVisual(moves[i], r);
+        this.play(moves[i]);
+        if (i < moves.length - 1) setTimeout(() => animateRec(i+1), 300);
+        else callback();
+      });
+    };
+    animateRec(0);
+  }
+
+};
diff --git a/common.css b/common.css
new file mode 100644
index 0000000..c0dba37
--- /dev/null
+++ b/common.css
@@ -0,0 +1,225 @@
+body {
+  margin: 0;
+  text-align: center;
+  background-color: #f8f8f8;
+  font-family:  Arial, Verdana, Tahoma, sans-serif;
+}
+
+#gameInfos, #boardContainer, #gameStopped, #pendingSeek, #pendingRematch, #newGameForm {
+  display: none;
+}
+
+#gameStopped > h1 {
+  margin-bottom: 10px;
+}
+
+/* Sticky footer */
+footer {
+  position: absolute;
+  bottom: 0;
+  left: 0;
+  right: 0;
+  height: 50px;
+}
+
+button {
+  background-color: green;
+  border: none;
+  color: white;
+  padding: 10px 15px;
+  text-align: center;
+  text-decoration: none;
+  display: inline-block;
+  font-size: 1em;
+  cursor: pointer;
+  border-radius: 20%;
+  margin: 15px 0;
+}
+
+button:hover {
+  background-color: darkblue;
+}
+
+button.block-btn {
+  display: block;
+  margin: 30px auto 20px auto;
+  font-size: 1.5em;
+  padding: 15px 32px;
+}
+
+#upLeftInfos {
+  position: absolute;
+  left: 0;
+  top: 0;
+}
+
+#upRightStop {
+  position: absolute;
+  left: calc(100% - 25px);
+  top: 0;
+}
+
+#upLeftInfos > img, #upRightStop > img {
+  width: 25px;
+  cursor: pointer;
+}
+
+#ng-select {
+  margin-bottom: 20px;
+}
+
+#ng-name {
+  /* TODO */
+}
+
+/* Options when starting custom game */
+.word {
+  cursor: pointer;
+  padding: 3px;
+}
+.highlight-word {
+  background-color: lightblue;
+}
+
+/* Game link div + custom game "button" */
+#gameLink span, #gameLink a, #playCustom {
+  text-decoration: underline;
+  color: blue;
+  cursor: pointer;
+}
+
+#selectVariant {
+  margin-right: 15px;
+}
+
+/* Board container (without reserves) */
+#chessboard {
+  position: absolute;
+  cursor: pointer;
+}
+
+/* Board container can be resized */
+.resizeable {
+  resize: both;
+  overflow: hidden;
+  min-width: 200px;
+  min-height: 200px;
+}
+
+piece {
+  position: absolute;
+  top: 0;
+  left: 0;
+  background-size: cover;
+  z-index: 2;
+  will-change: transform;
+  pointer-events: none;
+}
+
+/* Drawing of the board */
+#chessboard_SVG {
+  width: 100%;
+  height: 100%;
+}
+
+.reserves {
+  position: absolute;
+  display: block;
+  cursor: pointer;
+}
+
+.reserve-cell {
+  position: relative;
+  display: block;
+  float: left;
+}
+
+/* Pieces' counter for reserves */
+.reserve-num {
+  color: red;
+  position: absolute;
+  display: block;
+  font-weight: bold;
+  /*z-index: 10;*/
+}
+
+/* Choices div after a promotion (TODO: do not hide board) */
+#choices, .choice {
+  position: absolute;
+  cursor: pointer;
+}
+
+/* https://theanam.github.io/css-only-loaders/ ("hour-glass") */
+:root{
+  --loader-width: 70px;
+  --loader-height: 70px;
+  --loader-color-primary: #141D58;
+  --loader-color-secondary: #EEE;
+  --line-width: 3px;
+  --animation-duration: 3s;
+  --loader-initial-scale: 0.1;
+}
+.loader,.loader:before,.loader:after{
+  box-sizing: border-box;
+  flex-grow: 0;
+  flex-shrink: 0;
+}
+
+@keyframes slide {
+  0% {
+    transform: translateY(0%);
+  }
+  25% {
+    transform: translateY(100%);
+  }
+  50% {
+    transform: translateY(100%);
+  }
+  75% {
+    transform: translateY(0%);
+  }
+  100% {
+    transform: translateY(0%);
+  }
+}
+
+@keyframes spin {
+  0% {
+    transform: rotate(0deg);
+  }
+  25% {
+    transform: rotate(0deg);
+  }
+  50% {
+    transform: rotate(180deg);
+  }
+  75% {
+    transform: rotate(180deg);
+  }
+  100% {
+    transform: rotate(360deg);
+  }
+}
+
+.loader.hour-glass {
+  position: relative;
+  width: var(--loader-width, 100px);
+  height: var(--loader-height, 100px);
+  background-color: var(--loader-color-primary, #00f);
+  -webkit-clip-path: polygon(0% 0%, 100% 0%, 50% 50%, 100% 100%, 0% 100%, 50% 50%);
+  clip-path: polygon(0% 0%, 100% 0%, 50% 50%, 100% 100%, 0% 100%, 50% 50%);
+  overflow: hidden;
+  animation: spin var(--animation-duration, 4s) infinite ease-in-out;
+  margin: 20px auto;
+}
+
+.hour-glass:before {
+  content: "";
+  position: absolute;
+  top: 0px;
+  left: 0px;
+  width: var(--loader-width, 100px);
+  height: 50%;
+  background-color: var(--loader-color-secondary, #eee);
+  animation: slide var(--animation-duration, 4s) infinite ease-in-out;
+}
diff --git a/favicon.ico b/favicon.ico
new file mode 120000
index 0000000..f6ff788
--- /dev/null
+++ b/favicon.ico
@@ -0,0 +1 @@
+assets/favicon.ico
\ No newline at end of file
diff --git a/index.html b/index.html
new file mode 100644
index 0000000..12253ed
--- /dev/null
+++ b/index.html
@@ -0,0 +1,85 @@
+<!DOCTYPE html>
+<html>
+
+  <head>
+    <meta charset="utf-8"/>
+    <title>xogo</title>
+    <meta name="viewport"
+          content="width=device-width, initial-scale=1"/>
+    <link id="_common_css"
+          rel="stylesheet" href="./common.css"/>
+  </head>
+
+  <body>
+    <div id="gameInfos"></div>
+    <div id="boardContainer"></div>
+    <div id="gameStopped">
+      <h1>Game over</h1>
+      <button id="rematchBtn"
+              onClick="sendRematch()">
+        Rematch
+      </button>
+      <button class="cancel-something"
+              onClick="cancelRematch()">
+        Close
+      </button>
+    </div>
+    <div id="pendingRematch">
+      <div class="loader hour-glass"></div>
+      <button class="cancel-something"
+              onClick="cancelRematch()">
+        Cancel
+      </button>
+    </div>
+    <div id="newGame">
+      <button id="seekGame"
+              class="block-btn"
+              onClick="seekGame()">
+        Play!
+      </button>
+      <div id="ng-select">
+        <select id="selectVariant"></select>
+        <span id="playCustom"
+              onClick="showNewGameForm()">
+          Customize
+        </span>
+      </div>
+      <div id="ng-name">
+        <label for="myName">Name:</label>
+        <input id="myName"
+               type="text"
+               onChange="setName()"/>
+      </div>
+      <footer>
+        <a href="https://discord.gg/QC7Aa5WMYp">Discord</a>
+        /
+        <a href="https://github.com/yagu0/xogo">GitHub</a>
+      </footer>
+    </div>
+    <div id="pendingSeek">
+      <div class="loader hour-glass"></div>
+      <button class="cancel-something"
+              onClick="cancelSeek()">
+        Cancel
+      </button>
+    </div>
+    <div id="newGameForm">
+      <fieldset>
+        <label for="selectColor">Play as</label>
+        <select id="selectColor">
+          <option value=""></option>
+          <option value="w">Player 1</option>
+          <option value="b">Player 2</option>
+        </select>
+      </fieldset>
+      <fieldset id="gameOptions"></fieldset>
+      <button onClick="getGameLink()">Get link</button>
+      <button onClick="backToNormalSeek()">Cancel</button>
+      <div id="gameLink"></div>
+    </div>
+
+    <script src="/parameters.js"></script>
+    <script src="/variants.js"></script>
+    <script src="/app.js"></script>
+  </body>
+</html>
diff --git a/package-lock.json b/package-lock.json
new file mode 100644
index 0000000..7f52ea0
--- /dev/null
+++ b/package-lock.json
@@ -0,0 +1,40 @@
+{
+  "name": "xogo",
+  "lockfileVersion": 2,
+  "requires": true,
+  "packages": {
+    "": {
+      "dependencies": {
+        "ws": "^7.5.3"
+      }
+    },
+    "node_modules/ws": {
+      "version": "7.5.5",
+      "resolved": "https://registry.npmjs.org/ws/-/ws-7.5.5.tgz",
+      "integrity": "sha512-BAkMFcAzl8as1G/hArkxOxq3G7pjUqQ3gzYbLL0/5zNkph70e+lCoxBGnm6AW1+/aiNeV4fnKqZ8m4GZewmH2w==",
+      "engines": {
+        "node": ">=8.3.0"
+      },
+      "peerDependencies": {
+        "bufferutil": "^4.0.1",
+        "utf-8-validate": "^5.0.2"
+      },
+      "peerDependenciesMeta": {
+        "bufferutil": {
+          "optional": true
+        },
+        "utf-8-validate": {
+          "optional": true
+        }
+      }
+    }
+  },
+  "dependencies": {
+    "ws": {
+      "version": "7.5.5",
+      "resolved": "https://registry.npmjs.org/ws/-/ws-7.5.5.tgz",
+      "integrity": "sha512-BAkMFcAzl8as1G/hArkxOxq3G7pjUqQ3gzYbLL0/5zNkph70e+lCoxBGnm6AW1+/aiNeV4fnKqZ8m4GZewmH2w==",
+      "requires": {}
+    }
+  }
+}
diff --git a/package.json b/package.json
new file mode 100644
index 0000000..b02fc5e
--- /dev/null
+++ b/package.json
@@ -0,0 +1,5 @@
+{
+  "dependencies": {
+    "ws": "^7.5.3"
+  }
+}
diff --git a/parameters.js.dist b/parameters.js.dist
new file mode 100644
index 0000000..c1e3eb5
--- /dev/null
+++ b/parameters.js.dist
@@ -0,0 +1,16 @@
+const Params = {
+
+  // Usage on client:
+  http_server: "http://localhost:8000", //https://xogo.live
+  socket_server: "ws://localhost:8080", //wss://xogo.live
+
+  // Usage on (socket) server:
+  socket_port: 8080, //...
+
+  // Usage on both:
+  socket_path: "/ws",
+
+};
+
+// Next line for usage on server (Node.js)
+if (typeof window === 'undefined') module.exports = Params;
diff --git a/server.js b/server.js
new file mode 100644
index 0000000..c21d8bf
--- /dev/null
+++ b/server.js
@@ -0,0 +1,214 @@
+const params = require("./parameters.js");
+const WebSocket = require('ws');
+const wss = new WebSocket.Server(
+  {port: params.socket_port, path: params.socket_path});
+
+let challenges = {}; //variantName --> socketId, name
+let games = {}; //gameId --> gameInfo (vname, fen, players, options)
+let sockets = {}; //socketId --> socket
+const variants = require("./variants.js");
+
+const send = (sid, code, data) => {
+  const socket = sockets[sid];
+  // If a player delete local infos and then try to resume a game,
+  // sockets[oppSid] will probably not exist anymore:
+  if (socket) socket.send(JSON.stringify(Object.assign({ code: code }, data)));
+}
+
+const Crypto = require('crypto')
+function randomString(size = 8) {
+  return Crypto.randomBytes(size).toString('hex').slice(0, size);
+}
+
+wss.on('connection', function connection(socket, req) {
+  const sid = req.url.split("=")[1]; //...?sid=...
+  sockets[sid] = socket;
+  socket.isAlive = true;
+  socket.on('pong', () => socket.isAlive = true);
+
+  function launchGame(vname, players, options) {
+    const gid = randomString(8);
+    games[gid] = {
+      vname: vname,
+      players: players.map(p => {
+                 return (!p ? null : {sid: p.sid, name: p.name});
+               }),
+      options: options
+    };
+    if (players.every(p => p)) {
+      const gameInfo = Object.assign(
+        // Provide seed so that both players initialize with same FEN
+        {seed: Math.floor(Math.random() * 1984), gid: gid},
+        games[gid]);
+      for (let i of [0, 1]) {
+        send(players[i].sid, "gamestart",
+             Object.assign({randvar: players[i].randvar}, gameInfo));
+      }
+    }
+    else {
+      // Incomplete players array: do not start game yet
+      send(sid, "gamecreated", {gid: gid});
+      // If nobody joins within a minute, delete game
+      setTimeout(
+        () => {
+          if (games[gid] && games[gid].players.some(p => !p))
+            delete games[gid];
+        },
+        60000
+      );
+    }
+  }
+
+  socket.on('message', (msg) => {
+    const obj = JSON.parse(msg);
+    switch (obj.code) {
+      // Send challenge (may trigger game creation)
+      case "seekgame": {
+        // Only one challenge per player:
+        if (Object.keys(challenges).some(k => challenges[k].sid == sid))
+          return;
+        let opponent = undefined,
+            choice = undefined;
+        const vname = obj.vname,
+              randvar = (obj.vname == "_random");
+        if (vname == "_random") {
+          // Pick any current challenge if any
+          const currentChalls = Object.keys(challenges);
+          if (currentChalls.length >= 1) {
+            choice =
+              currentChalls[Math.floor(Math.random() * currentChalls.length)];
+            opponent = challenges[choice];
+          }
+        }
+        else if (challenges[vname]) {
+          opponent = challenges[vname];
+          choice = vname;
+        }
+        if (opponent) {
+          delete challenges[choice];
+          if (choice == "_random") {
+            // Pick a variant at random in the list
+            const index = Math.floor(Math.random() * variants.length);
+            choice = variants[index].name;
+          }
+          // Launch game
+          let players = [
+            {sid: sid, name: obj.name, randvar: randvar},
+            opponent
+          ];
+          if (Math.random() < 0.5) players = players.reverse();
+          launchGame(choice, players, {}); //empty options => default
+        }
+        else
+          // Place challenge and wait. 'randvar' indicate if we play anything
+          challenges[vname] = {sid: sid, name: obj.name, randvar: randvar};
+        break;
+      }
+      // Set FEN after game was created
+      case "setfen":
+        games[obj.gid].fen = obj.fen;
+        break;
+      // Send back game informations
+      case "getgame": {
+        if (!games[obj.gid]) send(sid, "nogame");
+        else send(sid, "gameinfo", games[obj.gid]);
+        break;
+      }
+      // Cancel challenge
+      case "cancelseek":
+        delete challenges[obj.vname];
+        break;
+      // Receive rematch
+      case "rematch": {
+        if (!games[obj.gid]) send(sid, "closerematch");
+        else {
+          const myIndex = (games[obj.gid].players[0].sid == sid ? 0 : 1);
+          if (!games[obj.gid].rematch) games[obj.gid].rematch = [false, false];
+          games[obj.gid].rematch[myIndex] = true;
+          if (games[obj.gid].rematch[1-myIndex]) {
+            // Launch new game, colors reversed
+            launchGame(games[obj.gid].vname,
+                       games[obj.gid].players.reverse(),
+                       games[obj.gid].options);
+          }
+        }
+        break;
+      }
+        // Rematch cancellation
+      case "norematch": {
+        if (games[obj.gid]) {
+          const myIndex = (games[obj.gid].players[0].sid == sid ? 0 : 1);
+          send(games[obj.gid].players[1-myIndex].sid, "closerematch");
+        }
+        break;
+      }
+      // Create game vs. friend
+      case "creategame":
+        let players = [
+          { sid: obj.player.sid, name: obj.player.name },
+          undefined
+        ];
+        if (
+          obj.player.color == 'b' ||
+          (obj.player.color == '' && Math.random() < 0.5)
+        ) {
+          players = players.reverse();
+        }
+        launchGame(obj.vname, players, obj.options);
+        break;
+      // Join game vs. friend
+      case "joingame": {
+        if (!games[obj.gid]) send(sid, "jointoolate");
+        else {
+          // Join a game (started by some other player)
+          const emptySlot = games[obj.gid].players.findIndex(p => !p);
+          if (emptySlot < 0) send(sid, "jointoolate");
+          games[obj.gid].players[emptySlot] = {sid: sid, name: obj.name};
+          const gameInfo = Object.assign(
+            // Provide seed so that both players initialize with same FEN
+            {seed: Math.floor(Math.random()*1984), gid: obj.gid},
+            games[obj.gid]);
+          for (let i of [0, 1])
+            send(games[obj.gid].players[i].sid, "gamestart", gameInfo);
+        }
+        break;
+      }
+      // Relay a move + update games object
+      case "newmove": {
+        // TODO?: "pingback" strategy to ensure that move was transmitted
+        games[obj.gid].fen = obj.fen;
+        const playingWhite = (games[obj.gid].players[0].sid == sid);
+        const oppSid = games[obj.gid].players[playingWhite ? 1 : 0].sid;
+        send(oppSid, "newmove", { moves: obj.moves });
+        break;
+      }
+      // Relay "game ends" message
+      case "gameover": {
+        const playingWhite = (games[obj.gid].players[0].sid == sid);
+        const oppSid = games[obj.gid].players[playingWhite ? 1 : 0].sid;
+        if (obj.relay) send(oppSid, "gameover", { gid: obj.gid });
+        games[obj.gid].over = true;
+        setTimeout( () => delete games[obj.gid], 60000 );
+        break;
+      }
+    }
+  });
+  socket.on("close", () => {
+    delete sockets[sid];
+    for (const [key, value] of Object.entries(challenges)) {
+      if (value.sid == sid) {
+        delete challenges[key];
+        break; //only one challenge per player
+      }
+    }
+  });
+});
+
+const interval = setInterval(() => {
+  wss.clients.forEach((ws) => {
+    if (ws.isAlive === false) return ws.terminate();
+    ws.isAlive = false;
+    ws.ping();
+  });
+}, 30000);
+wss.on('close', () => clearInterval(interval));
diff --git a/start.sh b/start.sh
new file mode 100755
index 0000000..4fe6790
--- /dev/null
+++ b/start.sh
@@ -0,0 +1,10 @@
+#!/bin/sh
+
+nodemon -i index.js -i base_rules.js ./server.js &
+echo "NODE_PID=$!" > .pid
+
+# NOTE: require browser plugin + start it
+livereload -e 'html,js,css,png,jpg,jpeg,gif,svg' -w 1000 -d . &
+
+# I use 8080 for socket and 8000 for http server (arbitrary...)
+php -S localhost:8000 &
diff --git a/stop.sh b/stop.sh
new file mode 100755
index 0000000..8d54dcc
--- /dev/null
+++ b/stop.sh
@@ -0,0 +1,5 @@
+#!/bin/sh
+
+# https://stackoverflow.com/questions/13939038/how-do-you-run-a-command-for-each-line-of-a-file
+source ./.pid
+kill -9 -`ps p $NODE_PID -o pgid | grep "[0-9]\+" | tr -d " "`
diff --git a/utils/Move.js b/utils/Move.js
new file mode 100644
index 0000000..62eddea
--- /dev/null
+++ b/utils/Move.js
@@ -0,0 +1,12 @@
+// class "Move": generic ready-to-play verbose move, standardised format.
+export default class Move {
+  // o: {appear, vanish, [start,] [end,]}
+  // appear,vanish = arrays of PiPo
+  // start,end = coordinates to apply to trigger move visually (think castle)
+  constructor(o) {
+    this.appear = o.appear;
+    this.vanish = o.vanish;
+    this.start = o.start || { x: o.vanish[0].x, y: o.vanish[0].y };
+    this.end = o.end || { x: o.appear[0].x, y: o.appear[0].y };
+  }
+};
diff --git a/utils/PiPo.js b/utils/PiPo.js
new file mode 100644
index 0000000..8d55134
--- /dev/null
+++ b/utils/PiPo.js
@@ -0,0 +1,10 @@
+// class "PiPo": Piece + Position
+export default class PiPo {
+  // o: {piece[p], color[c], posX[x], posY[y]}
+  constructor(o) {
+    this.p = o.p;
+    this.c = o.c;
+    this.x = o.x;
+    this.y = o.y;
+  }
+};
diff --git a/utils/alea.js b/utils/alea.js
new file mode 100644
index 0000000..8b5a4ea
--- /dev/null
+++ b/utils/alea.js
@@ -0,0 +1,44 @@
+// https://stackoverflow.com/a/47593316/12660887
+function mulberry32(a) {
+	return function() {
+		let t = a += 0x6D2B79F5;
+		t = Math.imul(t ^ t >>> 15, t | 1);
+		t ^= t + Math.imul(t ^ t >>> 7, t | 61);
+		return ((t ^ t >>> 14) >>> 0) / 4294967296;
+	}
+}
+
+export const Random = {
+
+  rand: null,
+
+  setSeed: function(a) {
+    Random.rand = mulberry32(a);
+  },
+
+  randInt: function(min, max) {
+    if (!max) {
+      max = min;
+      min = 0;
+    }
+    if (!Random.rand)
+      Random.setSeed(Math.floor(Math.random() * 1984));
+    return Math.floor(Random.rand() * (max - min)) + min;
+  },
+
+  // Inspired by https://github.com/jashkenas/underscore
+  sample: function(arr, n) {
+    n = n || 1;
+    let cpArr = arr.map(e => e);
+    for (let index = 0; index < n; index++) {
+      const rand = randInt(index, arr.length);
+      [ cpArr[index], cpArr[rand] ] = [ cpArr[rand], cpArr[index] ];
+    }
+    return cpArr.slice(0, n);
+  },
+
+  shuffle: function(arr) {
+    return sample(arr, arr.length);
+  }
+
+};
diff --git a/utils/array.js b/utils/array.js
new file mode 100644
index 0000000..8f2ebfe
--- /dev/null
+++ b/utils/array.js
@@ -0,0 +1,12 @@
+export const ArrayFun = {
+
+  // Double array intialization
+  init: function(size1, size2, initElem) {
+    return [...Array(size1)].map(() => Array(size2).fill(initElem));
+  },
+
+  range: function(max) {
+    return [...Array(max).keys()];
+  }
+
+};
diff --git a/variants.js b/variants.js
new file mode 100644
index 0000000..fb77f1d
--- /dev/null
+++ b/variants.js
@@ -0,0 +1,163 @@
+const variants = [
+/*  { name: 'Absorption', desc: 'Absorb powers' },
+  { name: 'Alapo', desc: 'Geometric Chess' },
+  { name: 'Alice', desc: 'Both sides of the mirror' },
+  { name: 'Align4', desc: 'Align four pawns' },
+  { name: 'Allmate', desc: 'Mate any piece' },
+  { name: 'Ambiguous', desc: "Play opponent's pieces" },
+  { name: 'Antiking1', desc: 'Keep antiking in check', disp: 'Anti-King' },
+  { name: 'Antimatter', desc: 'Dangerous collisions', disp: 'Antimatter' },
+  { name: 'Apocalypse', desc: 'The end of the world' },
+  { name: 'Arena', desc: 'Middle battle' },
+  { name: 'Atarigo', desc: 'First capture wins', disp: 'Atari-Go' },
+  { name: 'Atomic', desc: 'Explosive captures' },
+  { name: 'Avalam', desc: 'Build towers' },
+  { name: 'Avalanche', desc: 'Pawnfalls' },
+  { name: 'Ball', desc: 'Score a goal' },
+  { name: 'Balaklava', desc: 'Meet the Mammoth' },
+  { name: 'Bario', desc: 'A quantum story' },
+  { name: 'Baroque', desc: 'Exotic captures' },*/
+  { name: "Benedict", desc: "Change colors" },
+/*  { name: 'Berolina', desc: 'Pawns move diagonally' },
+  { name: 'Bicolour', desc: 'Harassed kings' },
+  { name: 'Bishopawns', desc: 'Bishop versus pawns', disp: 'Bishop-Pawns' },
+  { name: 'Brotherhood', desc: 'Friendly pieces' },
+  { name: 'Cannibal', desc: 'Capture powers' },
+  { name: 'Capablanca', desc: 'Capablanca Chess', disp: 'Capablanca Chess' },
+  { name: 'Capture', desc: 'Mandatory captures' },
+  { name: 'Castle', desc: 'Win by castling long' },
+  { name: 'Chakart', desc: 'Capture the princess' },
+  { name: 'Checkered', desc: 'Shared pieces' },
+  { name: 'Checkless', desc: 'No-check mode' },
+*/  { name: 'Chess960', disp: "Chess 960", desc: "Standard rules" },
+/*  { name: 'Circular', desc: 'Run forward' },
+  { name: 'Clorange', desc: 'A Clockwork Orange', disp: 'Clockwork Orange' },
+  { name: 'Convert', desc: 'Convert enemy pieces' },
+  { name: 'Copycat', desc: 'Borrow powers' },
+  { name: 'Coregal', desc: 'Two royal pieces' },
+  { name: 'Coronation', desc: 'Long live the Queen' },
+  { name: 'Crazyhouse', desc: 'Captures reborn' },
+  { name: 'Crossing', desc: 'Cross the river' },
+  { name: 'Cylinder', desc: 'Neverending rows' },
+  { name: 'Cwda', desc: 'New teams', disp: 'Different armies' },
+  { name: 'Dark', desc: 'In the shadow' },
+  { name: 'Diamond', desc: 'Rotating board' },
+  { name: 'Dice', desc: 'Roll the dice' },
+  { name: 'Discoduel', desc: 'Enter the disco', disp: 'Disco Duel' },
+  { name: 'Dobutsu', desc: "Let's catch the Lion!" },
+  { name: 'Doublearmy', desc: '64 pieces on the board', disp: 'Double Army' },
+  { name: 'Doublemove', desc: 'Double moves' },
+  { name: 'Dynamo', desc: 'Push and pull' },
+  { name: 'Eightpieces', desc: 'Each piece is unique', disp: '8-Pieces' },
+  { name: 'Emergo', desc: 'Stacking Checkers variant' },
+  { name: 'Empire', desc: 'Empire versus Kingdom' },
+  { name: 'Enpassant', desc: 'Capture en passant', disp: 'En-passant' },
+  { name: 'Evolution', desc: 'Faster development' },
+  { name: 'Extinction', desc: 'Capture all of a kind' },
+  { name: 'Fanorona', desc: 'Malagasy Draughts' },
+  { name: 'Football', desc: 'Score a goal' },
+  { name: 'Forward', desc: 'Moving forward' },
+  { name: 'Freecapture', desc: 'Capture both colors', disp: 'Free Capture' },
+  { name: 'Fugue', desc: 'Baroque Music' },
+  { name: 'Fullcavalry', desc: 'Lancers everywhere', disp: 'Full Cavalry' },
+  { name: 'Fusion', desc: 'Fusion pieces (v1)' },
+  { name: 'Gomoku', desc: 'Align five stones' },
+  { name: 'Grand', desc: 'Big board' },
+  { name: 'Grasshopper', desc: 'Long jumps over pieces' },
+  { name: 'Gridolina', desc: 'Jump the borders' },
+  { name: 'Hamilton', desc: 'Walk on a graph' },
+  { name: 'Hidden', desc: 'Unidentified pieces', disp: 'Strate-Go' },
+  { name: 'Hiddenqueen', desc: 'Queen disguised as a pawn', disp: 'Hidden Queen' },
+  { name: 'Hoppelpoppel', desc: 'Knibis and Bisknis', disp: 'Hoppel-Poppel' },
+  { name: 'Horde', desc: 'A pawns cloud' },
+  { name: 'Hypnotic', desc: 'Mind control (v1)' },
+  { name: 'Iceage', desc: 'Ice Age is coming!', disp: 'Ice Age' },
+  { name: 'Interweave', desc: 'Interweaved colorbound teams' },
+  { name: 'Isardam', desc: 'No paralyzed pieces' },
+  { name: 'Janggi', desc: 'Korean Chess' },
+  { name: 'Joker', desc: 'Replace pieces' },
+  { name: 'Karouk', desc: 'Thai Chess (v3)', disp: 'Kar-Ouk' },
+  { name: 'Kinglet', desc: 'Protect your pawns' },
+  { name: 'Kingsmaker', desc: 'Promote into kings' },
+  { name: 'Knightmate', desc: 'Mate the knight' },
+  { name: 'Knightpawns', desc: 'Knight versus pawns', disp: 'Knight-Pawns' },
+  { name: 'Knightrelay', desc: 'Move like a knight' },
+  { name: 'Konane', desc: 'Hawaiian Checkers' },
+  { name: 'Koopa', desc: 'Stun & kick pieces' },
+  { name: 'Koth', desc: 'King of the Hill', disp:'King of the Hill' },
+  { name: 'Losers', desc: 'Get strong at self-mate' },
+  { name: 'Madhouse', desc: 'Rearrange enemy pieces' },
+  { name: 'Madrasi', desc: 'Paralyzed pieces' },
+  { name: 'Magnetic', desc: 'Laws of attraction' },
+  { name: 'Maharajah', desc: 'Augmented Queens' },
+  { name: 'Makpong', desc: 'Thai Chess (v2)' },
+  { name: 'Makruk', desc: 'Thai Chess (v1)' },
+  { name: 'Maxima', desc: 'Occupy the enemy palace' },
+  { name: 'Mesmer', desc: 'Mind control (v2)' },
+  { name: 'Minishogi', desc: 'Shogi 5 x 5' },
+  { name: 'Minixiangqi', desc: 'Xiangqi 7 x 7' },
+  { name: 'Monocolor', desc: 'All of the same color' },
+  { name: 'Monster', desc: 'White move twice' },
+  { name: 'Musketeer', desc: 'New fairy pieces' },
+  { name: 'Newzealand', desc: 'Kniros and Rosknis', disp: 'New-Zealand' },
+  { name: 'Omega', desc: 'A wizard in the corner' },
+  { name: 'Orda', desc: 'Mongolian Horde (v1)' },
+  { name: 'Ordamirror', desc: 'Mongolian Horde (v2)', disp: 'Orda Mirror' },
+  { name: 'Otage', desc: 'Capture and release hostages' },
+  { name: 'Pacifist', desc: 'Convert & support' },
+  { name: 'Pacosako', desc: 'Dance with the King', disp: 'Paco-Sako' },
+  { name: 'Pandemonium', desc: 'Noise and confusion' },
+  { name: 'Parachute', desc: 'Landing on the board' },
+  { name: 'Pawnmassacre', desc: 'Pieces upside down', disp: 'Pawn Massacre' },
+  { name: 'Pawns', desc: 'Reach the last rank (v1)' },
+  { name: 'Pawnsking', desc: 'Reach the last rank (v2)', disp: 'Pawns & King' },
+  { name: 'Perfect', desc: 'Powerful pieces' },
+  { name: 'Pocketknight', desc: 'Knight in pocket', disp: 'Pocket Knight' },
+  { name: 'Progressive', desc: 'Play more and more moves' },
+  { name: 'Queenpawns', desc: 'Queen versus pawns', disp: 'Queen-Pawns' },
+  { name: 'Racingkings', desc: 'Kings cross the 8x8 board', disp: 'Racing Kings' },
+  { name: 'Rampage', desc: 'Move under cover' },
+  { name: 'Relayup', desc: 'Upgrade pieces', disp: 'Relay-up' },
+  { name: 'Rifle', desc: 'Shoot pieces' },
+  { name: 'Recycle', desc: 'Reuse pieces' },
+  { name: 'Refusal', desc: 'Do not play that!' },
+  { name: 'Rollerball', desc: 'As in the movie' },
+  { name: 'Rococo', desc: 'Capture on the edge' },
+  { name: 'Rookpawns', desc: 'Rook versus pawns', disp: 'Rook-Pawns' },
+  { name: 'Royalrace', desc: 'Kings cross the 11x11 board', disp: 'Royal Race' },
+  { name: 'Rugby', desc: 'Transform an essay' },
+  { name: 'Schess', desc: 'Seirawan-Harper Chess', disp: 'Seirawan-Harper Chess' },
+  { name: 'Screen', desc: 'Free initial setup' },
+  { name: 'Selfabsorb', desc: 'Fusion pieces (v2)', disp: 'Self-Absorption' },
+  { name: 'Shako', desc: 'Non-conformism and utopia' },
+  { name: 'Shatranj', desc: 'Ancient rules' },
+  { name: 'Shinobi', desc: 'A story of invasion' },
+  { name: 'Shogi', desc: 'Japanese Chess' },
+  { name: 'Shogun', desc: "General's Chess" },
+  { name: 'Sittuyin', desc: 'Burmese Chess' },
+  { name: 'Spartan', desc: 'Spartan versus Persians' },
+  { name: 'Squatter', desc: 'Squat last rank' },
+  { name: 'Stealthbomb', desc: 'Beware the bomb', disp: 'Stealth Bomb' },
+  { name: 'Suicide', desc: 'Lose all pieces' },
+  { name: 'Suction', desc: 'Attract opposite king' },
+  { name: 'Swap', desc: 'Dangerous captures' },
+  { name: 'Switching', desc: "Exchange pieces' positions" },
+  { name: 'Synchrone', desc: 'Play at the same time' },
+  { name: 'Synochess', desc: 'Dynasty versus Kingdom' },
+  { name: 'Takenmake', desc: 'Prolongated captures', disp: 'Take and make' },
+  { name: 'Teleport', desc: 'Reposition pieces' },
+  { name: 'Tencubed', desc: 'Four new pieces' },
+  { name: 'Threechecks', desc: 'Give three checks', disp: 'Three Checks' },
+  { name: 'Titan', desc: 'Extra bishops and knights' },
+  { name: 'Twokings', desc: 'Two kings', disp: 'Two Kings' },
+  { name: 'Upsidedown', desc: 'Board upside down', disp: 'Upside-down' },
+  { name: 'Vchess', desc: 'Pawns capture backward', disp: 'Victor Chess' },
+  { name: 'Wildebeest', desc: 'Balanced sliders & leapers' },
+  { name: 'Wormhole', desc: 'Squares disappear' },
+  { name: 'Xiangqi', desc: 'Chinese Chess' },
+  { name: 'Yote', desc: 'African Draughts' },*/
+  { name: "Zen", disp: "Zen Chess", desc: "Reverse captures" }
+];
+
+// Next line for usage on server (Node.js)
+if (typeof window === 'undefined') module.exports = variants;
diff --git a/variants/Benedict/class.js b/variants/Benedict/class.js
new file mode 100644
index 0000000..c0fffcc
--- /dev/null
+++ b/variants/Benedict/class.js
@@ -0,0 +1,98 @@
+import ChessRules from "/base_rules.js";
+import PiPo from "/utils/PiPo.js";
+
+export default class BenedictRules extends ChessRules {
+
+  static get Options() {
+    return {
+      select: ChessRules.Options.select,
+      check: [],
+      styles: (
+        ChessRules.Options.styles.filter(s => {
+          return (
+            ["balance", "cylinder", "dark", "doublemove", "progressive", "zen"]
+            .includes(s)
+          );
+        })
+      )
+    };
+  }
+
+  get hasEnpassant() {
+    return false;
+  }
+
+  get pawnSpecs() {
+    return Object.assign(
+      {},
+      super.pawnSpecs,
+      { canCapture: false }
+    );
+  }
+
+  canTake() {
+    return false;
+  }
+
+  // Find potential captures from a square
+  // follow steps from x,y until something is met.
+  findAttacks([x, y]) {
+    const [color, piece] = [this.getColor(x, y), this.getPiece(x, y)];
+    const oppCol = ChessRules.GetOppCol(color);
+    let squares = {};
+    const specs = this.pieces(color)[piece];
+    const steps = specs.attack || specs.steps;
+    outerLoop: for (let step of steps) {
+      let [i, j] = [x + step[0], this.computeY(y + step[1])];
+      let nbSteps = 1;
+      while (this.onBoard(i, j) && this.board[i][j] == "") {
+        if (specs.range <= nbSteps++) continue outerLoop;
+        i += step[0];
+        j = this.computeY(j + step[1]);
+      }
+      if (this.onBoard(i, j) && this.getColor(i, j) == oppCol)
+        squares[ChessRules.CoordsToSquare({x: i, y: j})] = true;
+    }
+    return Object.keys(squares);
+  }
+
+  postProcessPotentialMoves(moves) {
+    if (moves.length == 0) return moves;
+    const [x, y] = [moves[0].end.x, moves[0].end.y];
+    const color = this.getColor(moves[0].start.x, moves[0].start.y);
+    const oppCol = ChessRules.GetOppCol(color);
+    moves = super.postProcessPotentialMoves(moves);
+    moves.forEach(m => {
+      this.playOnBoard(m);
+      let attacks;
+      if (this.options["zen"]) {
+        let endSquares = {};
+        super.getZenCaptures(x, y).forEach(c => {
+          endSquares[ChessRules.CoordsToSquare(c.end)] = true;
+        });
+        attacks = Object.keys(endSquares);
+      }
+      else attacks = this.findAttacks([m.end.x, m.end.y])
+      this.undoOnBoard(m);
+      attacks.map(ChessRules.SquareToCoords).forEach(a => {
+        const p = this.getPiece(a.x, a.y);
+        m.appear.push(new PiPo({x: a.x, y: a.y, c: color, p: p}));
+        m.vanish.push(new PiPo({x: a.x, y: a.y, c: oppCol, p: p}));
+      });
+    });
+    return moves;
+  }
+
+  // Moves cannot flip our king's color, so (almost) all are valid
+  filterValid(moves) {
+    if (this.options["balance"] && [1, 3].includes(this.movesCount))
+      return moves.filter(m => m.vanish.every(v => v.p != ChessRules.KING));
+    return moves;
+  }
+
+  // Since it's used just for the king, and there are no captures:
+  underCheck(square, color) {
+    return false;
+  }
+
+};
diff --git a/variants/Benedict/rules.html b/variants/Benedict/rules.html
new file mode 100644
index 0000000..0211f6b
--- /dev/null
+++ b/variants/Benedict/rules.html
@@ -0,0 +1 @@
+<a href="https://www.chessvariants.com/difftaking.dir/benedict.html">Benedict rules</a>.
diff --git a/variants/Benedict/style.css b/variants/Benedict/style.css
new file mode 100644
index 0000000..9378e29
--- /dev/null
+++ b/variants/Benedict/style.css
@@ -0,0 +1 @@
+@import "../../base_pieces.css"
diff --git a/variants/Chess960/class.js b/variants/Chess960/class.js
new file mode 100644
index 0000000..abafb56
--- /dev/null
+++ b/variants/Chess960/class.js
@@ -0,0 +1,3 @@
+import ChessRules from "/base_rules.js";
+
+export default class Chess960Rules extends ChessRules {};
diff --git a/variants/Chess960/rules.html b/variants/Chess960/rules.html
new file mode 100644
index 0000000..46751e1
--- /dev/null
+++ b/variants/Chess960/rules.html
@@ -0,0 +1 @@
+<a href="https://en.wikipedia.org/wiki/Rules_of_chess">Orthodox chess rules</a>.
diff --git a/variants/Chess960/style.css b/variants/Chess960/style.css
new file mode 100644
index 0000000..9378e29
--- /dev/null
+++ b/variants/Chess960/style.css
@@ -0,0 +1 @@
+@import "../../base_pieces.css"
diff --git a/variants/Zen/class.js b/variants/Zen/class.js
new file mode 100644
index 0000000..f06dd1f
--- /dev/null
+++ b/variants/Zen/class.js
@@ -0,0 +1,18 @@
+import ChessRules from "/base_rules.js";
+
+export default class ZenRules extends ChessRules {
+
+  static get Options() {
+    return {
+      select: ChessRules.Options.select,
+      check: ChessRules.Options.check,
+      styles: ChessRules.Options.styles.filter(s => s != "zen")
+    };
+  }
+
+  constructor(o) {
+    super(o);
+    o.options.zen = true;
+  }
+
+};
diff --git a/variants/Zen/rules.html b/variants/Zen/rules.html
new file mode 100644
index 0000000..569f213
--- /dev/null
+++ b/variants/Zen/rules.html
@@ -0,0 +1,3 @@
+<p>Pieces capture enemy units which threaten them (normal captures are disabled).</p>
+
+<p>Exception: the king is attacked as usual.</p>
diff --git a/variants/Zen/style.css b/variants/Zen/style.css
new file mode 100644
index 0000000..9378e29
--- /dev/null
+++ b/variants/Zen/style.css
@@ -0,0 +1 @@
+@import "../../base_pieces.css"