If you don't know what Nexrun is, it's a physics set which is based on CPM physics. These allow for something called strafejumping and circle strafing etc, which both gain you great amounts of speed in the game.
Nexrun CTS however, (CTS = Complete This Stage) is all about finishing a map in as little time as possible with the Nexrun physics.
Check out the Nexrun CTS movie to see for yourself!
Youtube: http://www.youtube.com/watch?v=ssTkc3Hgbzo
Higher quality: http://hrfdesign.com/crap/videos/nexrunmovie.ogv (need some mirrors!)
To play these maps yourself, you can either connect to a Nexrun CTS server or download the two following files:
Demos, configs, scripts: http://hrfdesign.com/nexrun/nexrun_v1r1.pk3
Mappack: http://hrfdesign.com/nexrun/nexrun_maps_v1r1.zip
You can find the individual maps here (plus some others that did not make it into the "official" release): http://hrfdesign.com/nexrun/index.php?dir=maps-repo%2F
There's also some preliminary defrag compatibility being worked on (the configs are included with the first zip, and there is a script for waypointing them)
Compat pack for all currently supported (and waypointed) defrag maps: http://hrfdesign.com/nexrun/nexrun_defr ... t_v1r1.zip
Note that the compat pack only includes the ent file, mapinfo and mapshot. Get the map pk3s manually from q3a.ath.cx (or just connect to the [NL] Nexrun CTS server, as it runs these maps)

Individual defrag compat files: http://hrfdesign.com/nexrun/index.php?dir=defrag%2F
Major problems that still exist with defrag maps:
- No automatic race waypoints
- On some maps, the start line is solid in Nexuiz, which prevents the player from even playing the map (let alone play a manually waypointed map like it was supposed to be played in defrag)

- No slick support
- Lots of missing textures
- Wrong player entity size (can't fit through some holes etc)
Our irc channel is at #nexrun @ irc.quakenet.org