Chess variant with only pawns (not even kings), and that player wins who first moves a pawn to the opposite side of the board.
Otherwise the rules of chess apply, with the following difference:
The number of the pawns are adjustable. For more pawn lines, only the pawns on the (usual) second rank can make a double-move.
Please note that if the player on turn has pawns but no legal moves, it is a stalemate, i.e. draw.