World four hundred and twenty-two is with ten boxes for placement on the upper and the left walls.
Step by step solution
Go UP, UP, LEFT, LEFT, push DOWN and DOWN. Go LEFT, LEFT, DOWN, push LEFT, LEFT, go DOWN, LEFT, push UP, UP, UP and UP. Go DOWN, DOWN, DOWN, RIGHT, RIGHT, RIGHT, UP, RIGHT, RIGHT, push DOWN and DOWN. Go UP, UP, UP, UP, RIGHT, RIGHT, DOWN, DOWN, DOWN, push LEFT, go DOWN, LEFT, push UP and UP. Go DOWN, RIGHT, RIGHT, UP, UP, UP, LEFT, LEFT and push LEFT. Go UP, LEFT, LEFT, push DOWN, DOWN and DOWN.
Go RIGHT, DOWN, push LEFT, LEFT, go DOWN, LEFT, push UP, UP and UP. Go DOWN, DOWN, RIGHT, RIGHT, UP, UP, UP, UP, RIGHT, RIGHT, DOWN, push LEFT, go UP, LEFT and push DOWN. Go RIGHT, RIGHT, RIGHT, RIGHT, RIGHT, DOWN, DOWN, DOWN, LEFT, LEFT, UP, LEFT, LEFT, push UP, UP, go LEFT, UP and push RIGHT. Go DOWN, DOWN, DOWN, LEFT, push UP and UP. Go DOWN, DOWN, RIGHT, RIGHT, RIGHT and push UP.
Go DOWN, DOWN, RIGHT, RIGHT, UP, UP, UP, LEFT, push LEFT, LEFT, go RIGHT, DOWN, DOWN, LEFT, LEFT, UP and push UP. Go RIGHT, RIGHT, RIGHT, RIGHT, DOWN, DOWN, push LEFT, LEFT, LEFT, LEFT, go UP, LEFT, push DOWN, go RIGHT, DOWN, push LEFT, LEFT, go DOWN, LEFT, push UP and UP. Go DOWN, RIGHT, RIGHT, RIGHT, DOWN and push LEFT. Go RIGHT, UP, UP, RIGHT, RIGHT, DOWN, DOWN and push LEFT.
Go DOWN, DOWN, RIGHT, push UP, UP, UP, go RIGHT, UP, push LEFT, LEFT and LEFT. Go DOWN, LEFT, DOWN and push RIGHT. Go LEFT, UP, LEFT, LEFT, DOWN and push RIGHT. Go UP, RIGHT, RIGHT, UP, UP, LEFT, push DOWN, go RIGHT, DOWN, push LEFT, LEFT, go DOWN, LEFT and push UP.
Go RIGHT, RIGHT, RIGHT, DOWN, push LEFT and LEFT. Go RIGHT, RIGHT, push RIGHT, go DOWN, RIGHT, push UP, UP, go RIGHT, UP, push LEFT, LEFT, LEFT, go UP, LEFT, push DOWN, go RIGHT, DOWN, push LEFT and LEFT.
Congratulations. You have completed world four hundred and twenty-two. Get ready for world four hundred and twenty-three.