The Rubik's Hypercube is a generalization of the regular Rubik's Cube into 4-dimensional space.  The Rubik's Hypercube program shows a 3-dimensional "unfolded" version of this 4-dimensional object.  Though I wrote the Rubik's Hypercube program, I have not solved the harder version of it.  I have solved the easier version, and I plan to soon put up a list of hints for solving it.  If you solve the harder version, please email me at berglund@math.gatech.edu, and if you can remember what you did, try to explain it.  I will post good hints I receive on the hints page, along with their author(s).  To download the zip file for installing the latest version of Rubik's Hypercube, click
Download Rubik's Hypercube(416K). 

Rubik's Hypercube allows you to create a high-score file. Unfortunately, my program for reading a high-score file was destroyed in a hard-drive failure, so if you solve the Rubik's Hypercube and want to be listed in the high scores table, please email me the .rhc file. Your score will then be posted on the High Scores Webpage. 

Other cool sites involving the 4th dimension
Mark Newbold'sJava Stuff - Java applets depicting rotating 4-dimensional hypercubes and other cool stuff like that
HyperCube by Harmen - A stereoscopic game involving a hypercube(Java applet)
Special Relativity - Learn about special relativity and solutions to time-space paradoxes.
Fourth Dimension - A Web page about the 4th dimension
Other 4-dimensional Rubik's Cubes
MagicCube4D	4DimensionRubikCube

The Rubik's Hypercube program is also availible at nonags.com, plus lots of other cool freeware.