''At just about every turn, Braid thumbs its nose at your expectations.
To hear one describe it, you'd think that it's all been done before, but the approach in this 2-D platformer title is fresh and new. The player journeys through a series of five worlds in Braid, collecting puzzle pieces along the way. The platforming sequences pay homage to everyone's template, Super Mario Bros. As expected, various enemies, ladders, locked doors, and harrowing jumping sequences try to obstruct your progress from point A to point B.
You don't need to have all of the puzzle pieces to finish a world, but you will need all of them to complete the game. You won't be able to reach some of the puzzle pieces until you unlock new abilities near the end of the game. At that point, you can revisit the appropriate worlds with your new-found skills to obtain the previously unreachable items. The level selection screen helpfully displays the number of puzzle pieces that still remain in each world, so you don't have to needlessly revisit any locales.
Time behaves differently in each world, and you'll have to exercise your noggin to understand how time is moving in each world so that you can figure out how you'll need to manipulate time to accomplish your goals. You may shrug this off as having been done in Prince of Persia, but after some reflection, you'll admit that the time-reversal mechanic in PoP is optional and is merely a way of fixing your mistakes, whereas time manipulation is vital to each of Braid's worlds. Time may flow normally in one world, whereas another world has time moving forward when you go to the right and backward when you go to the left.''