Braid's protagonist, Tim, is a young man searching for a princess, whom he has wronged in some way. In his quest, Tim has to collect a variety of puzzle pieces in order to progress throughout the game and unlock subsequent stages.
At first glance, Braid might seem like your typical side-scroller, but it also incorporates a set of unique mechanics dealing with time. Not only can you reverse time to stop yourself from dying (after you fall in a pit, for example), but in many cases, the manipulation of time is for solving the puzzles. Further levels add additional gameplay tweaks, such as time slowing down, or even playing in a sort of parallel "shadow" universe.
Add to that some gorgeous graphics that border on impressionist paintings and a terrific soundtrack, and it's easy to see how Braid has walked away with a number of awards in 2008, including Xbox Magazine's Xbox Live Arcade Game of the Year.
Braid's available , where you can download the demo or buy the full game for $15. The game requires either the latest version of either Mac OS X 10.4 or 10.5; a 1.0GHz or better G4, G5, or Intel-based Mac; 512MB of RAM; and at least an Nvidia GeForce FX 5900, ATI Radeon 9500, or Intel GMA 950 graphics chip.