cube 2 is a complete redesign of the cube engine developed by Wouter "Aardappel" van Oortmerssen.
This engine is really something special, I've seen some incredible things done with it. It has a simple premise but it is so much more. It allows for both things that are incredibly simple but fun and things that are amazingly complex.
Games that run on it perform great, at least I've never had any problems even on my older PC that could barely run most games Sauerbraten for example ran at very stable 45+ FPS.