Use the arrow keys to control the player and avoid the attacks and use z to look up. After finishing the first wave of attacks the boss will repeat his last 3 attacks until he is hurt enough, in which case he will stop attacking. How to clear the first wave of attacks; avoid the first attack while staying off to the side of the screen. Then wait on the side of the screen for his second attack to finish. Once you can tell it has stopped run to the center of the screen so you can more easily dodge the missiles. Go back to the center of the screen and when the giant hand is one step away from you run under it and follow it back to the far right side of the screen, where you are safe from the laser. After this, you can shelter under the platforms while avoiding the missiles for all of the attacks except for the laser, which you have to run to the far right to avoid.
