http://www.incitti.com/Blitz/
Top item "Grid Wars" is a Geometry Wars clone for the PC. Very fun.
Admiral: They updated it yesterday, and now it has crazy warping grids in the background.
Anyway get it while it's available. I've heard things like MS is going to send a cease and desist order, since it's an exact clone, or something to that effect.
Everyone grab this while you can...
Moderator: enderzero