- : Use the direction pad to control Amagon (or Megagon) throughout the game. Press left or right to make Amagon run in either direction. Press down to make Amagon squat.
- : Press the A button to make Amagon jump into the air. The longer you hold down the A button, the higher he will jump.
- : Press the B button to make Amagon shoot his gun. If Amagon is out of ammunition, press the B button to swing his gun like a club. If you are currently in Megagon form, press the B button to throw a punch.
- : Press the Start button to begin a new game, or to pause the action mid-game.
- : If you have collected the Megagon power-up and have the word "Go!" flashing next to your ammunition count at the top of the screen, press the Select button to transform Amagon into Megagon.
You begin the game as Amagon, shown to the left. He has crashed his plane on an island, and must cross the island to reach the rescue ship waiting for him. He must survive his journey across the island. Amagon cannot survive contact with any of the creatures that he finds on the island. If he touches them, or any of the projectiles they fire, he will lose one life. If he loses all of his lives, the game ends, and there are no chances to continue unless you he has reached round 4-1.
Amagon is armed with a gun which he can fire at the various creatures on the island. Amagon can only fire his weapon as long as he has ammunition. If he runs out of ammo, he is not defenseless; he can swing his gun like a club, but he must be close to creatures in order to hit them. As Amagon attacks enemies, he will receive various items from them in the form of item tiles (see below). Many of these tiles are points, but he can also receive ammunition, extra lives, and the tile which grants him the power to transform into the powerful Megagon.
To transform into Megagon, you must collect the power-up tile, and then press . Once this happens, Amagon will grow in size and power. At this time, some of your score in converted into health for Megagon. For every 5000 points, Megagon will gain one bar of health. This is applied for a maximum of 70,000 points, at which point Megagon will have 14 bars of health. Any time Megagon is touched or shot by an enemy, he will lose one bar of health. If Megagon loses all of his health, he will transform back into Amagon. If Megagon completes a level with any health remaining, each bar of health is transformed back into 5000 points. If, however, Megagon loses all of his health, you will lose all of the points.
As Megagon, not only can you survive contact with creatures, you can also deal powerful blows with your fists. Each punch is the equivalent of eight bullets. When he punches enemies, he will not receive any item tiles. However, Megagon has one additional attack. By holding and pressing , Megagon will swing his arm and launch a mega wave attack and destroys enemies. Creatures killed in this fashion may drop tiles. However, for every mega wave that you fire, you will lose one bar of health. You will be unable to use this attack if Megagon has no health remaining.