Stackers

Each turn, a player can place a piece consisting of three triangles on the lowest level, the second lowest, etc., until he adds a new level or passes. No two adjacent triangles can have the same colour, but all stacked triangles should have the same colour.
Once there are nine levels, stacked pieces can extend beyond the horizontal limits of the base board. (Even pieces that are placed on lower levels.)

The player who first manages to play all his pieces, wins.