Instructions
Equip the Cane of Pacci and jump or run away from Vaati when he tries to hit Link with his arms. Run right or left to avoid the fireballs that he will throw periodically.
Use the Cane of Pacci to hit Vaati's arms when they emerge through the floor. When the arms fully appear, run to the top of the screen and jump on the shrink box. Run back to the arm and enter the tiny doorway.
Run towards the eyeballs and use your sword to hit the one that has a different eye color than the rest. When that eyeball dies, the others will disappear. Exit the room and head back to the shrink box. Run into the small door and Link will grow to his normal size.
Repeat steps two and three to destroy Vaati's arms.
Charge your sword and run right or left to avoid the electric attacks thrown by the armless Vaati.
Move Link to the bottom of the screen until he is next to four squares. When Vaati charges his four eyes, walk Link across the four squares and he will duplicate himself until there are four Links in total.
Use your charged sword to knock the four electric balls back at Vaati. Run to him and hit him with the uncharged sword until four new eyes appear.
Repeat steps 5, 6 and 7 to defeat Vaati and beat the game.