· There is an undocumented option available that switches the planes into UFO's. Pin 14 of the 003127 IC (a PROM located at grid location K1) is tied to ground (at Pin 8 of K2), but also has a pull-up resistor. Cutting the ground trace causes address bit A4 to be pulled high, selecting the UFO data. A jumper can be installed to easily switch back and forth between planes and UFO's. The UFO version of the game was probably never released.