2008: Demo: SystemK - Life on Air
graphical difficulty: 7-9/10 (seems to run better on nvidia. is probably poorly coded)
design: 7/10 (imo. i really like bright, colorful things)
2009: 4K: Rgba - Elevated
graphical difficulty: 8/10
design: 8/10 (strictly from a graphics to filesize standpoint 9.5/10)
note: probably will trigger antivirus; see comments for windows 7 fix (or run CRINKLER.EXE /recompress input.exe)
if you can get 50+fps with this, you must have a freakin' beast of a machine. is available in 3D in-demo and on youtube.
2008: 4K: Archee - Photon Race 2
graphical difficulty: 11/10
design: 7/10
rayyyyyyytracing!!! also, like the other 4K, could trigger a/v. may have to use CRINKLER.EXE /recompress input.exe if a win7 fix can't be found.