This opensource game is built on an entirely new an very unconventional engine. Cube is a landscape-style engine that pretends to be an indoor FPS engine, which combines very high precision dynamic occlusion culling with a form of geometric mipmapping on the whole world for dynamic LOD for configurable fps & graphic detail. Most of the engine design is targeted at reaching feature richness through simplicity of structure and brute force, rather than finely tuned complexity.
This iPhone port is provided by fernLightning and it supports all of the functionality of the desktop version including multiplayer, in-game editing, cooperative editing, demo recording, etc.
Cube is a free application and is available starting today in the Apple App Store.