Spair is a very simple two players game playable with two Shibumi game systems. It uses two 4×4 boards, and two whole sets of balls.
Rules
The board starts empty. Two players take turns placing a ball of one color on the first board (called A), and then a ball of another color on the second board (called B), according to the following rules:
1) a ball may be placed on a board if its color is different from the color of the ball that has been placed on the same board in the previous turn and
2) a player must place a ball of the color not placed by the opponent in the previous turn.
Balls may be placed either on empty board holes or stacking on 2x2 platforms of existing balls.
A player wins when a full line of any single color is made, orthogonally or diagonally, on any level on his board: board B for the first player and board A for the second player.
Lines on the 4x4 (board) level must be of length 4, lines on the 3x3 level must be of length 3, and lines on the 2x2 level must be of length 2.