Well blow me down. This game named Braid and it's creator Jonathon Blow are getting a lot of positive buzz lately. Joystiq spoke of Jonathon at GDC as the Messiah, walking around surrounded by admirers.
Check out his game, it sounds fascinating.
The levels are filled with standard 2D-platform elements: stationary and moving platforms; "goombas" walking to and fro; cannons spitting out fireballs (or goombas) at regular intervals; long jumps over pits full of spikes; and even green pipes with snapping piranha plants poking out. In terms of its level elements, Braid makes nod after nod to that platform game of all platform games, Super Mario Bros. The story line follows suit, using SMB's princess rescue as a metaphor for the main character's pursuit of an ideal romantic partner.
Totally standard platformer. The game is broken up into 6 worlds, actually starting in the 2nd world where the game introduces a Prince of Persia-esque rewind feature.
If you take the hint that the game gives you, you will try pressing the Shift key, and you will be greeted with wonderful sights and sounds: the game rewinds time right before your eyes. The background animations, the goombas, and all of your previous actions move backward. Even the music plays in reverse. You un-die, and up you un-fall, out of the spikes and back onto the platform from whence you jumped. If you let go of Shift, you're ready to try that jump again. If you keep holding down shift, you can rewind back through all of your actions, right back to the point where you entered the level. Everything can be undone.
Not a big deal... yet.
In World 3, time works the same as it does in World 2, with the addition of "purple sparkle objects." These objects, like the key and the gate pictured below, are immune to the rewind button. For example, if your character falls down into an inescapable pit, the rewind button can be used to rescue your character by allowing him to un-fall back out of the pit. If he grabs a purple-sparkle key while down there, however, the key will remain in his hand while he un-falls, and he will carry the key up out of the pit.
Now it gets interesting:
World 4 introduces a totally different time model: the world's position in time is directly linked to your character's position in space. As your character walks to the right, time goes forward. As he walks left, time goes backward. While he stands still, time stops. Hitting the rewind button causes your character's actions to rewind, which can cause the surrounding world's time to go both forward and backward (depending on which way he moves during the rewind).
In World 5, time's behavior becomes even more interesting. Pressing the rewind button to undo an action spawns a "alternate universe" in which an alternate version of your character still carries out the action that you just rewound.
World 6 cools things down a bit with a somewhat simpler time model: your character is equipped with a ring that he can drop and pick up at will. The spot where the ring is dropped becomes a locus of time slow-down. For your character, and the rest of the objects in the world, time progresses at a rate proportional to the distance between these object and the ring.
After World 6, if you have collected all the puzzle pieces in Worlds 2 through 6, you'll be able to enter World 1 (recall that the game starts in World 2). In this final world, time moves backward for all objects, excluding your character. Goombas walk backward and un-die instantly after you jump on them. Fireballs retreat back into cannons.
I'd buy that.