Braid

World 3 is the second world you'll have access to in the game. The levels aren't too difficult but now anything with a green aura is immune to your time travel abilities. Once you finish all the levels you'll unlock the achievement.

There are 8 levels with a total of 12 puzzle pieces.
The Pit (No Pieces)
There and Back Again (1 Puzzle Piece)
Phase (2 Puzzle Pieces)
The Ground Beneath Her Feet (2 Puzzle Pieces)
Tight Channels (2 Puzzle Pieces)
Irreversible (3 Puzzle Pieces)
Lair (No Pieces)
A Tingling (2 Puzzle Pieces)

See the achievement "Solved World 3" for help on completing the level/getting all puzzle pieces.