p.boxed
  | Similar to Checkers, with prisoners stacked below capturers.

p
  | The 9x9 board is initially empty.
  | Each player receives 12 stackable pieces, "in hand".
  | At each turn, a player must either
  ul
    li.
      Enter a new piece on the board such that the opponent cannot capture it.
      However, if a capture is already possible before the move, then
      the piece can be dropped anywhere.
      White cannot place a piece in the center at move 1.
    li Play a move on the board, along diagonals.

p.
  Simple moves are Ferz moves: one step diagonally.
  Captures work exactly as in Checkers: by jumping over a diagonally adjacent
  piece to land on a free square just behind.
  However, the resulting situation is more complex. See below.
  If a capture is possible, then it must be played; in this case no piece can
  be introduced on the board.

p TODO: diagram

p.
  Let us consider each unit as a compound entity containing W white pieces
  and B black ones (initially W = 1 and B = 0 for white units,
  and vice-versa for black).
  Captures can then be described formally as follows.

p.
  As white:
  If W1/B1 jumps over W2/B2 at square S2 to land on S1', then
  W1/(B1+1) arrives on S1' and W2/(B2-1) remains on S2.
  If W2 = B2 - 1 = 0, nothing remains at the captured unit location.
  As black: exchange W and B above.

p.
  In other words, each unit is a stack of friendly and enemy pieces, with
  friendly pieces on top. After each capture, the prisoners part of the
  stack is incremented, while the "jailers" counterpart at the captured
  location decreases by one.

p.
  When several capturing chains are available,
  the player has to select one of the longest (as in Checkers).

p TODO: diagram (from mindsports.nl)

h3 More information

p
  | See the 
  a(href="https://www.mindsports.nl/index.php/arena/emergo/88-rules")
    | Emergo page
  |  on the author's website.
  | Rules are also described on 
  a(href="http://www.iggamecenter.com/info/en/emergo.html") iggamecenter
  | , where you can also play this game.

p Inventors: Christian Freeling and Ed van Zon (1986)