Lunatic Fringe is the eleventh level and the second secret level that can be found in the episode Lunar Apocalypse of the game Duke Nukem 3D. The player can get to this level if they find the secret exit in Dark Side.
Lunatic Fringe is quite a short level that mostly takes place in a large circular area; it appears to be some sort of alien space station or possibly a former EDF space station that was overrun. However for its size, the resistance is quite fearsome as Duke Nukem will have to fight a few battlelord sentries in the central room. There are two main areas in Lunatic Fringe; the outer circle and an inner room; the inner room being the area where the battlelord sentries are; Duke can open up the central area by pushing all the buttons beside the large screens which is quite similar to how the center is opened in Spin Cycle, but unlike Spin Cycle, it's less complex as there aren't as many buttons and this level doesn't finish in the center; it finishes off in a small hallway that Duke gets into by being shrunk after hitting a button in the center. The music is quite creepy too!
- This level is famous for its revolutionary, non-euclidean geometry: the appears to be a simple circle, but player was required to run 720 degrees around it before they can get back to the starting point, which really did show just how revolutionary the Build engine is. Later games have achieved it, but the game engine wasn't designed for it in mind, resulting in minor imperfections.
- The idea of the '720 degree circle' is probably inspired by Stephen Hawking's view of so-called spin ½ particles, like electrons or quarks, "that do not look the same if one turns them through just one revolution: you have to turn them through two complete revolutions!" 
- The level appears to be named after the Red Rider song which was also called Lunatic Fringe.
- Use DNSHOWMAP to enable the whole map. Zoom out using '-' and on the edge of the map you will find 'SUYT'. DNCLIP will allow you to run all the way out to it.
- ↑ Hawking, A brief history of time, 1988