Shooting some of these unmoving aliens turns them into gems (that you collect) and some turn into blue crystallized aliens (that you cannot be destroyed). You are searching for a path through the maze of aliens as the board scrolls down. You try to avoid shots from the aliens or any other pointy bits or flames and more importantly, try not to be caught behind anything as the screen scrolls. Either will kill you and the game -- on one death! -- will be over. However, you get to keep the gems you collect and upgrade your ship with better defences, shooting, or mobility. And if you get through the other side of the alien maze you can fight the boss in a typical shoot 'em up bullet hell.