Ride your music
Essentially a "match the colours" styled puzzle game with an ingenious hook. The levels are generated by and stylised to any music track (multi-format compatible) that you choose. Similar to Guitar Hero without the axe, but the ability to groove along to any tune in your library.
The track for each song is always the same and you can compete with others seamlessly online on a track by track basis. The way that the gameplay is synchronised to the chosen music is quite amazing, especially considering that tracks are produced "on the fly" in only a few seconds. There are 3 difficulty tiers and many player characters which allow full customisation of the experience to your mood and style.
Rack up the points on a rolling meandering ballad, or scream, loop and twist through some speed metal - it all depends on what you choose to play. As I write this, Steam has secured digital distribution rights to the game, so expect a lot more interest in this title as well as increased competition in the more popular songs. Addictive, conceptually ground-breaking and technically stunning, Audiosurf is just a "must-play" on so many levels and a steal at just $9.95