Magic Cube 4D

If you're on the lookout for a new headache-inducing puzzle, then look no further! This four-dimensional version of a Rubik's cube has
1,756,772,880,709,135,843,168,526,079,081,
025,059,614,484,630,149,557,651,477,156,
021,733,236,798,970,168,550,600,274,887,
650,082,354,207,129,600,000,000,000,000
possible combinations, so you can imagine that it'll take quite a while to solve. :-)

For more information, see the project's home page. Linux and Windows versions are available.