This is a prototype low-cost optical tile based touchscreen interface, primarily intended for simple game/toy applications. The white translucent tiles are illuminated by a grid of RGB LEDs. Tiny ball bearings inserted into the corners of each tile help the tiles to glide over the screen's surface, while also gently sticking to it magnetically. The presence and location of the tiles is detected by sequentially flashing the RGB LEDs very brightly - but very briefly (so as to be unnoticed by the user). If enough light is reflected back towards the reverse-biased green 3mm LED positioned next to each RGB LED, then a tile is detected at that location. (The 3mm green LEDs were selected as photosensors because after testing a great many different type of LED components from various suppliers, these were found to be particularly light sensitive and low cost.) I am currently updating the microcontroller and writing new games applications for this prototype. All game suggestions wel