Once in the game, using the arrow keys you can move the 'Scanner' ship around the 'Shield Line' at the parameter of the playing area. While moving around this edge the ship is protected from the aliens by a shield indicated by a glowing circle around the ship. This shield is not infinite and care should be taken to complete each level as quickly as possible. A counter indicates the level of shield that you have: when it reaches zero then any contact with an alien is deadly whether you are on the 'Shield Line' or not. The idea of the game is to cut areas out of the screen without touching any of the aliens. This is done by pressing the SPACE key which initiates the 'Laser Cutter' and moving off the 'Shield Line' and rejoining it somewhere else. While you are in the process of drawing a line, your shield is inactive and touching an alien is fatal. Similarly, if one of the aliens touches the line then it will send a charge down the line towards you and you must quickly return to the safety of the edge before it reaches you. When you rejoin the 'Shield Line' the area that does not contain the 'Boss' alien will be filled (points are gained by trapping the other aliens) and the 'Shield Line' will be adjusted to surround the area that is left. The level is completed when a certain percentage of the total area has been filled in. This percentage starts at 80% but may increase in the later levels.