A classic logic puzzle involves delineating a set of dominoes that has been arranged within a grid. Here, a grid is given on the left, and the full set of double-5 dominoes is given in a triangular array on the right. As lines between squares are clicked, dominoes in the triangular array will turn black when they are represented once, and red when they are represented more than once. Goal: turn all the dominoes in the triangular array black.