X-Git-Url: https://git.auder.net/?a=blobdiff_plain;f=views%2Frules%2FUpsidedown%2Fen.pug;h=8d4fa73beb1458f94ba05379883fffd231940a1e;hb=69f3d8014e594ef949792d04d97b8286e9c2c268;hp=695cbe4875828c5f53718a18025059aa87186b7b;hpb=dbcc32e95d526fe518ac866f7b3cdac546f1178e;p=vchess.git

diff --git a/views/rules/Upsidedown/en.pug b/views/rules/Upsidedown/en.pug
index 695cbe48..8d4fa73b 100644
--- a/views/rules/Upsidedown/en.pug
+++ b/views/rules/Upsidedown/en.pug
@@ -1,42 +1,32 @@
 p.boxed
 	| Pawns start on the 7th rank. Move a knight to promote them.
 
-Diagram: ... threatens Nc5-Nd3# and allow 2.b8=Q
+h3 Divergences
 
-figure.diagram-container
-	.diagram
-		| fen::
-	figcaption Standard initial position after 1.Na6
-
-h3 Specifications
-
-ul
-	li Chessboard: standard.
-	li Material: standard.
-	li Non-capturing moves: standard.
-	li Special moves: no castling (and no en-passant).
-	li Captures: standard.
-	li End of game: standard.
+p No castle, no en-passant capture.
 
 p.
-	...(Almost) Only the initial position changes, but this is a very big change.
+	...Only the initial position changes, but this makes a huge difference.
 	In particular, castling would be rather pointless so it's disabled here.
 	En-passant captures are impossible because all pawns already reached 7th rank.
 
-h3 Note on initial position
+h3 About the initial position
 
 p.
-	Since truly random start can allow un-defendable mate in 3 with a knight,
-	the kings touch at least one knight in the initial position.
+	Since truly random start can allow a mate in 3 with a knight,
+	the kings have at least one knight neighbor in the initial position.
 	This allows to move free out of potential check from the very beginning.
-	Here is an example:
 
-// TODO: diagram
+p.
+	A less constraining condition would be to require the two knights to stand on
+	two squares of different colors, but it's not enough as proved by the
+	following diagram.
+	White can mate in 3: 1.Nc6 followed by Nb4 threatening both a2 and d3.
+
 figure.diagram-container
 	.diagram
-		| fen:r7/2n5/1q6/5k2/8/8/K7/8:
-	figcaption.
-		The king cannot take on a8 because it's guarded by the knight: it's checkmate
+		| fen:RBN1BRRQ/PPPPPPP/8/4n3/8/8/Nppppppp/brkbqr1n:
+	figcaption After 1.Nc6 Nf3 2.Nb4 Ne5 (covers d3 but not a2) 3.Nxa2#
 
 h3 Source