Your mission is to protect the Trilithium Refineries on the planet Karthos. You pilot a Megan Class Scout Ship equipped with a Delta Laser. The enemy attacks grow more and more frequent as wave after wave of enemy missiles pass overhead. At all costs you must destroy the missiles before they reach the Refinery. Each missile will deplete the Refinery Shields until eventually they collapse. Your Scout Ship is fitted with landing, fuel and guidance computers. Your Control Panel also displays the status of the Refinery shield level. Your fuel is very limited and must be replenished frequently by landing on your base pad.