The Game Boy is the highest selling game platform in the world coming in many flavors from the GB, to GB Micro right up to the GBA SP. The GBA was the last of these released (now succeeded by the Nintendo DS).
The engine used to build this game was a once-off creation, designed explicitly to run this particular title. This is not a _real_ game engine, this is...
Doom+ is a modified version of IdTech1, It has many features and powers Hell On Earth.
This Engine Allows You To Make PT2 Icons and Effects and Maps.Plus The Maps Go in your map choosing area