World four hundred and one is with nine boxes, very close to each other.
Step by step solution
Push LEFT, go DOWN, LEFT, LEFT, UP, LEFT, push UP and UP. Go RIGHT, RIGHT and push RIGHT. Go UP, push UP, go LEFT, UP, LEFT, LEFT, LEFT, DOWN, DOWN and push RIGHT. Go LEFT, UP, UP, RIGHT, RIGHT, RIGHT, DOWN, push DOWN, go RIGHT, DOWN and push LEFT. Go UP, UP, UP, LEFT, LEFT, LEFT, DOWN, DOWN, RIGHT, push RIGHT, RIGHT, go UP, RIGHT and push DOWN. Go LEFT, LEFT, LEFT, DOWN, DOWN, DOWN, RIGHT, DOWN, RIGHT, RIGHT, UP and push LEFT.
Push UP, UP and UP. Go LEFT, LEFT, LEFT, UP, UP, RIGHT, RIGHT, RIGHT, UP, RIGHT and push DOWN. Go RIGHT, RIGHT, DOWN, DOWN, DOWN, RIGHT, DOWN, DOWN, push LEFT, LEFT, LEFT, go DOWN, LEFT, push UP and UP. Go DOWN, RIGHT, RIGHT, RIGHT, RIGHT, UP, UP, LEFT, UP, UP, UP, LEFT, LEFT, LEFT, LEFT, LEFT, LEFT, DOWN, DOWN, RIGHT, RIGHT, RIGHT, RIGHT and push RIGHT. Go LEFT and push UP. Go DOWN, LEFT, LEFT, LEFT, LEFT, UP, UP, RIGHT, RIGHT, RIGHT and push DOWN.
Go RIGHT, DOWN and push LEFT. Go UP, UP, LEFT, LEFT, LEFT, DOWN, DOWN, RIGHT, DOWN, DOWN, DOWN and push RIGHT. Go DOWN, RIGHT, RIGHT, UP and push LEFT. Go UP and push UP. Go DOWN, DOWN, RIGHT, RIGHT, RIGHT, RIGHT, UP, UP, LEFT and push UP. Go LEFT, LEFT, UP, LEFT and push DOWN. Go UP, UP, LEFT, LEFT, LEFT, DOWN, DOWN, RIGHT, push RIGHT and RIGHT. Go LEFT, LEFT, DOWN, DOWN, DOWN, push RIGHT, go DOWN, RIGHT, RIGHT, UP and push LEFT.
Go UP, push UP and UP. Go LEFT, LEFT, DOWN, DOWN, DOWN, push RIGHT, go DOWN, RIGHT, push UP and UP. Go DOWN, RIGHT, RIGHT, RIGHT, RIGHT, UP, UP, LEFT, UP, LEFT and push LEFT. Go RIGHT, RIGHT, DOWN, RIGHT, DOWN, DOWN, LEFT, LEFT, LEFT, LEFT, LEFT, LEFT, UP, UP, UP, LEFT, UP, UP, RIGHT, RIGHT, RIGHT, UP, RIGHT, push DOWN and DOWN. Go UP, RIGHT, RIGHT, push DOWN and DOWN.
Congratulations. You have completed world four hundred and one. Get ready for world four hundred and two.