A large slab of polished gray stone rests in a vast and colorless void. Seventeen small indentations are cut into it, arranged in the shape of a figure-eight. Eight white and eight black marbles are placed in these. The center hole where the two sides meet—the volta—is empty. This object has yet to achieve a definitive state.
The indentations on the left side of the figure-eight are numbered in counter-clockwise order. The indentations on the right side are numbered in clockwise order. The indent shared between both sides is the volta. It is the indent between the first and last numbered indent of each circle. A marble can only be moved by jumping it forward over to the vacant indent if there is one marble between it and the vacancy. Try swapping the white and black marbles.