This engine is the code behind "The game Creator's" FPS Creator development tool, A powerful, yet rough FPS engine.
I used to love this application when I was about 12. How are people still using this? It is outdated, basic and buggy as hell. If you want to make the most generic FPS game of all time then use this engine. If you want to make anything even slightly different, use something else, please. Unity is almost as easy to learn as this crap and 100x as flexible.