Rules

The board starts empty. Two players, white and red, take turns placing a ball of their colour either on a empty board hole or stacking on a 2x2 platform of existing balls.

A player, as an alternative, can choose to remove a ball (white or red) belonging to a 2x2 platform that supports not more than one other ball on each higher level. If a ball is removed then any others that it supports will drop. Any ball that directly supports two or more on the level above is pinned and cannot be removed. The removed ball must return immediately to the board in the place left free by the top ball just dropped (spinout rule, as for a car out of control!). A player is not allowed to remove a ball if the other player just removed a ball in his turn.

Aim: the goal of the game is to create the most three-in-a-rows on the surface of the Shibumi pyramid (4 triangular faces). Rows can intersect but do not wrap around corners or edges.
The game ends when the board is full with the 30 balls. Players are not allowed to pass and if a player has not legal moves the other player ends the game by placing his remaining balls to complete the pyramid.
In case of a tie for number of three-in-a-rows, the winner is the player who has the least number of balls on the surface of the pyramid.