World 5 wasn’t to bad, imo there are 3 tough puzzles and all are secret star puzzles. They are
World 4
World 6
World b+
These 3 without a doubt are the hardest things you will face in this game, these took me longer then the rest of the entire game, personally I thought all 3 of these puzzles were incredibly unfair, with the one in world 6 having insane pin-point perfect timing needed.