Heavy Unit

Destroyed enemies may leave behind items which have beneficial effects when collected: increased speed, better weapon power, a shield, extra lives or transformation into a robot. The robot has a more powerful weapons system (laser beam and homing energy balls instead of a vulcan gun), but also a downside: its large size makes it easier to be hit by enemies or crash into the environment. If that happens, a life and all collected upgrades are lost and the ship is reset at the last checkpoint.

While the level layouts are identical in all versions, there are some minor differences in enemy placement, graphics (e.g. the PC Engine version has more colours and bigger enemies) and sound.