p.boxed
  | A normal move is always followed by an opponent's pawn push.

p.
  Each turn consists of two parts. The first part is a move
  legal with the orthodox chess rules. The second part of the move,
  called "push", consists of moving an opponent's pawn a single space forward
  (toward the player in turn).
  White has no pawn push on the first move ("balanced" Avalanche).

p.
  If no pawn can advance at the second part, then it's
  opponent's turn. If a pushed pawn reaches its last rank,
  the opponent decides next in which piece it promotes.

figure.diagram-container
  .diagram.diag12
    | fen:rnbqkbnr/1pppp1pp/8/p7/P3Pp2/8/1PPPKPPP/RNBQ1BNR:
  .diagram.diag22
    | fen:rnbqkbnr/1pppp1pp/8/p7/P3P3/2N2p2/1PPPKPPP/R1BQ1BNR:
  figcaption.
    White plays Nc3,f3 (bad idea). Then Black can capture the king.

p In some cases, kings can be captured. This counts as a win.

p There are no en-passant captures.

h3 More information

p
  | See 
  a(href="https://www.chessvariants.com/mvopponent.dir/avalanche.html")
    | Avalanche Chess
  |  on chessvariants.com.

p Inventor: Ralph Betza (1977)