Another simple concept, it's a maze game where the walls aren't shown. Which would be simple enough, except that the walls are tagged with a colour. If you touch a wall, then only itself and the tiles marked with the same colour light up (and a distinct sound plays). So you need to move along and touch other parts of the maze to reveal the rest of the map. Of course you need to keep this in your mind because as soon as you leave the wall, everything goes dark again. Twisted!