When six different rank markers have been collected, the player advances a rank. When defeating a larger alien, there is the opportunity to collect a rank marker. The third level introduces larger versions of the aliens. The first two levels of a pack are levels containing only small aliens.
Levels are made in packs of four, with each pack introducing a new alien design. On defeating some aliens, random bonuses will be dropped for the player to collect, such as money, improved weaponry, Memory station, Meteor Storm, Gem Drop.
The player must defeat all the aliens on the screen by shooting at them from the ship to advance to the next level. An assembly of bug-like alien creatures fly onto the screen and shoot at the player's ship. The player controls a small ship, which moves along the bottom of the screen.
