BrainBoard - The objective is to remove as much pebbes as you can. The pebbles are arranged in four 3x3 grids and there is one empty 3x3 grid in the middle of the four grids. Removing a pebble is pretty simple; if you move a pebble to any adjacent empty cell of any nearby pebble, that nearby pebble will be removed. You cannot move or place a pebble diagonally