Spiral Nim is played on a 5x5 board with a rectangular spiral pattern.
Each player starts with four pieces. The pieces move through the spiral in the direction of the opponent pieces. A piece moves in a straight line and must travel until encountering a wall or another piece.
Opponent pieces are captured by replacement.
Players get two moves per turn, except that Red moves once at the opening. Passing is not allowed.
Win by capturing all four opponent pieces.