It is rumored that Jedi was a product of reverse-engineering the Doom engine to find out how to build their own. Jedi, was in the end more advanced than the Doom engine, containing features such as rooms over rooms, polygonal objects, haze and fog and the ability to look up and down. It also allowed designers to construct overlapping sectors ("room-over-room") to create multi-story buildings, bridges, and similar structures; earlier first-person shooter engines, such as Doom, do not support this ability. The Jedi Engine does not support perspective correction when looking up and down.