This game is played on an 8x8 square board, with a 2x2 square in the upper left hand of the board set aside as the 'Barn'. The players decide on the number of horses that will be used for the game (8 is a good number). At the beginning of the game, each player takes turns dropping one of those horses onto an empty cell.
On each turn, each player moves all of the horses (which move like chess knights but one player must move them west-west-north/south and the other player move them north-north-west/east). When a horse enters inside the barn it is removed from play. More than one horse can occupy a space at a time. If a player cannot move some horse on their turn, that player loses.
Diverse variants exist, e.g. impartial (all 4 possible moves for a horse are available to both players), misere play (the first player who cannot move a horse on their turn wins), etc.