The open source Zircon engine ("DarkPlaces Mark V Project") is a modification DarkPlaces engine with a mouse driven menu everywhere, ALT-ENTER fullscreen/windowed switching and 88 other enhancements to support user/mapper/mod coder ease-of-use and optional conveniences for those interested in a "1996 Quake" experience. "csqc_full_width_height 1" in console when running Arcane Dimensions at this time It is hoped that some/many/all of these enhancements will eventually make it into official DarkPlaces. The Zircon engine seeks to keep full compatibility with DarkPlaces so either engine can be used interchangeably.
Quake Combat+/Quake 1.5 issue with crash resolved -- Quake Combat+/Quake 1.5 perform autosaves very early in level load, Zircon was accessing rendering data before level had fully loaded -- and sometimes it would crash or not crash depending on the previous level loaded. Other changes see readme.