Braid

World 6 is the fifth world you'll have access to in the game. The levels are difficult as hell now, you get a ring that will make everything near it slower, this seems easier but since the game now wants you to have quick reflexes and perfect timing things can get tricky. Once you finish all the levels you'll unlock the achievement.

There are 7 levels with a total of 14 puzzle pieces.
The Pit? (No Pieces)
Phase? (2 Puzzle Pieces)
Cascade (3 Puzzle Pieces)
Impassible Foliage (3 Puzzle Pieces)
Movement by Degrees (2 Puzzle Pieces)
Elevator Action (3 Puzzle Pieces)
In Another Castle (1 Puzzle Pieces)

See the achievement "Solved World 6" for help on completing the level/getting all puzzle pieces.