Similar environment as Chess board and Tic-Tac-Toe, and Sudoku with both drawText(text, x, y, color, size) and registerOnClick but also adds a registerOnKeyDown that works like registerOnClick but registers a function that is called with the name of any key pressed while the drawing canvas has the focus. Of particular use for this game you can look for the key values 'ArrowRight', 'ArrowLeft', 'ArrowUp', and 'ArrowDown' indicating the arrow keys have been pressed.