World four hundred and fifty-one is average sized, very hard puzzle.
Step by step solution
Go UP, UP, RIGHT, push RIGHT, go DOWN, RIGHT and push UP. Go DOWN, RIGHT, DOWN, RIGHT, RIGHT, UP, push LEFT, LEFT and LEFT. Go RIGHT, RIGHT, RIGHT, UP, RIGHT, push DOWN, go RIGHT, DOWN, push LEFT, LEFT and LEFT. Go RIGHT, RIGHT, UP, UP, UP, UP, LEFT, UP, UP, RIGHT, push DOWN, DOWN, DOWN, DOWN, DOWN, go RIGHT, DOWN, push LEFT and LEFT. Go UP, LEFT, LEFT, LEFT, UP, LEFT, LEFT, LEFT, LEFT, UP, UP, push UP, go LEFT, UP, push RIGHT, RIGHT and RIGHT. Go DOWN, push RIGHT, RIGHT, RIGHT, RIGHT, RIGHT, go UP, RIGHT, push DOWN, DOWN, DOWN, DOWN, go LEFT, DOWN, LEFT, LEFT, LEFT, UP and push UP. Go RIGHT and push UP. Go DOWN, LEFT, DOWN, LEFT, LEFT, LEFT, LEFT, UP, UP, UP, UP, RIGHT, RIGHT, DOWN, RIGHT, RIGHT, push RIGHT, RIGHT and RIGHT.
Go DOWN, RIGHT, DOWN, DOWN, LEFT, DOWN, LEFT, LEFT, LEFT, DOWN, LEFT and push UP. Go RIGHT, RIGHT, RIGHT, RIGHT, DOWN, RIGHT, RIGHT, UP, push LEFT, LEFT, LEFT, LEFT and LEFT. Go UP, UP, RIGHT, UP, UP, RIGHT, RIGHT, UP, RIGHT, push DOWN, DOWN, DOWN, DOWN, go LEFT, DOWN, DOWN, RIGHT, RIGHT, UP, push LEFT and LEFT. Go RIGHT, UP, UP, UP, LEFT, UP, LEFT, LEFT, LEFT, LEFT, LEFT, UP, UP, RIGHT, push DOWN, go LEFT, DOWN, push RIGHT, RIGHT, RIGHT, RIGHT, RIGHT, go UP, RIGHT, push DOWN, DOWN, DOWN, DOWN, DOWN, go LEFT, DOWN and push RIGHT. Go UP, UP, UP, UP, LEFT, UP, LEFT, LEFT, DOWN, DOWN, LEFT, DOWN, DOWN, RIGHT and push RIGHT. Go LEFT, LEFT, UP, UP, RIGHT, UP, UP, RIGHT, RIGHT, DOWN, RIGHT, DOWN, DOWN, LEFT and push DOWN.
Go LEFT, LEFT, LEFT, UP, UP, RIGHT, UP, UP, LEFT, LEFT, LEFT, UP, LEFT, LEFT, DOWN, DOWN, DOWN, DOWN, RIGHT, DOWN, DOWN, LEFT, push UP, UP, UP, UP, UP, go LEFT, UP, push RIGHT, RIGHT, RIGHT, go UP, RIGHT, push DOWN, go LEFT, DOWN, push RIGHT, RIGHT, RIGHT, RIGHT, RIGHT, go UP, RIGHT, push DOWN, DOWN, DOWN, DOWN and DOWN. Go LEFT, LEFT, LEFT, LEFT, UP, push LEFT and LEFT. Go UP and push RIGHT. Go DOWN, RIGHT, DOWN, RIGHT, RIGHT, RIGHT, UP, RIGHT, UP, UP, LEFT, UP, LEFT, LEFT, LEFT, LEFT, LEFT, UP, LEFT, LEFT, DOWN, DOWN, DOWN and push RIGHT. Push DOWN, go RIGHT, RIGHT, UP and push LEFT. Go RIGHT, DOWN, RIGHT, DOWN, DOWN, LEFT, push UP, go RIGHT, UP and push LEFT. Go RIGHT, DOWN, RIGHT, RIGHT, RIGHT, UP, RIGHT, UP, UP, LEFT, UP, LEFT, LEFT, DOWN, DOWN and push LEFT.
Go RIGHT, UP, UP, LEFT, push DOWN, DOWN, DOWN and DOWN. Go UP, UP, UP, UP, LEFT, LEFT, UP, LEFT, LEFT, DOWN, DOWN, DOWN, DOWN, RIGHT, push RIGHT and RIGHT. Go LEFT, LEFT, LEFT, UP, UP, UP, UP, RIGHT, RIGHT, RIGHT, DOWN, RIGHT, DOWN, DOWN, push DOWN, go LEFT, DOWN, push RIGHT and RIGHT. Go LEFT, LEFT, UP, LEFT, UP and push RIGHT. Go LEFT, DOWN, LEFT, LEFT, UP, UP, UP, UP, RIGHT, RIGHT, RIGHT, DOWN, RIGHT, DOWN, push DOWN, DOWN, go LEFT, DOWN and push RIGHT. Go LEFT, UP, LEFT, LEFT, LEFT, UP, push RIGHT, RIGHT and RIGHT. Go LEFT, LEFT, LEFT, DOWN, DOWN, DOWN, RIGHT, push UP, go LEFT, UP, push RIGHT, RIGHT, go UP, RIGHT and push DOWN. Go LEFT, LEFT, LEFT, UP, UP, UP, UP, RIGHT, RIGHT, DOWN, RIGHT, RIGHT, DOWN, push DOWN and DOWN.
Congratulations. You have completed world four hundred and fifty-one. Get ready for world four hundred and fifty-two.