The Pie in the Sky engine's fairly popular predecessor game. Instead of being a first person shooter like the later games based on Pie in the Sky it is a flight simulator game. The game takes place in a world where Hitler died in childhood and World War II never happened. It its stead, aliens have invaded the Earth. The player must take control of a F4U Corsair, the only World War II plane that made it into this alternate history, and defeat the alien invaders. The game takes place in a variety of different locations and was noted for its original gameplay and presentaton. It is also known for being one of the few shareware flight simulators. Source: Wikipedia, "Pie in the Sky (game engine)", available under the CC-BY-SA License.