is a board game
invented by David G. Royffe and published by Gigamic
. Two players are given 15 marbles each. They take turns to make a pyramid in a 4 by 4 square grid (note that 15 × 2 = 4 × 4 + 3 × 3 + 2 × 2 + 1). Simple rules allow them to save their marbles — if possible, instead of playing a new marble, a player may rise one of his already played marbles to a higher position, and if any move forms a 2×2 square of marbles the player's colour, the player may (and indeed must) remove one or two of his marbles from the board. The winner is the player who completes the pyramid.