I refer more to the game logic on the original game engine. For example, there can't be bridges or rooms over other rooms. Or a flying monster can't be over oth

I refer more to the game logic on the original game engine. For example, there can't be bridges or rooms over other rooms. Or a flying monster can't be over other monster or a player. On other side, the original game engine, use 2d math with fixed point to rendering on a 386 CPU. Don't uses mvp matrix to render, like a real 3d game. Take a look to : http://doom.wikia.com/wiki/Doom_rendering_engine http://doom.wikia.com/wiki/Doom_rendering_engine