From the homepage at http://wouter.fov120.com/cube/
Landscape-style engine that pretends to be an indoor first person shooter engine. 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 on most machines.
Using OpenGL and SDL (Simple Direct Media Layer), this 3D engine is in fact a very capable gaming engine for multiplayer deathmatch games, and if you wish old-fashioned run around and kill stuff this is your friend. At writing time, the 8.63 megabyte free download with game binaries for both Windows and Linux/ LinuxPPC and servers for Linux, Solaris and FreeBSD from the homepage is very much worth it. There should also be a Mac OS X version, available from http://batteryacid.org/blog/ (May 25th, 2003), however I have not been able to test this, though people on the CUBE forum report it as working.
The engine is a masterpiece of usability. The editing of game maps is performed from within the game and can be done over the network (local or wide area) with more people editing the same map, according to the author the first engine to allow you to do so. Basically, you fly around the map in full 3D and edit it using your mouse to point and drag map elements. The simple map layout also means that with today's powerful computers you do not need to compile the maps, as they are simple enough to be both computed, rendered and lighted on the fly. Like UNIX applications should be, the game is designed around the KISS (Keep It Simple Stupid) programming principle, so rather than having a large set of very finely tuned exeptions to a rule like most modern game engines such as Quake and Unreal, the engine uses brute force to do a lot of things using one system.
To get help for the game in any way, either resort to the documentation on the homepage or in the archive or to the forum, or you can go onto the CUBE IRC channel #cube on irc.gamesnet.net