"Each world has a specific mechanic and overlapping rarely occurs between world mechanics. Instead, the player is given just enough objects on the screen to solve the puzzle with the limited tools available. By being able to concentrate on one mindset of solving the puzzle, eventually the solutions make themselves apparent." A nice Manveer Heir piece on why the puzzles themselves in Braid are good: because the game creates complexity out of limited tools, rather than throwing every mechanic in all the time.