Activator is a side-view flick-screen maze game, where you control an Activator Pod sent into the Space Port Antari found on the edge of the Sol Galaxy. An unknown power source has rendered any carbon based life-forms and their equipment inactive, and as the last of the power has emptied, a distress signal was sent out, and you have picked it up and found the Space Port's location from it. You are the Commander of a Federation Patrol and Space Port Protection Craft and when you have got close enough to Antari you have sent the Activator Pod inside. The Pod's aim, under your control, is to find fuel-rods to activate the power and place them in Room 97.

You can carry only three items at a time and other items you need to be aware of are bullets and key-passes. The bullets allow you to shoot and destroy the various aliens roaming the corridors of Antari and if you touch one the you lose part of a power gauge. When the gauge empties then you lose one of nine lives. The key-passes allow you to go through doors but both are labelled with letters from A to G and can only be used if the letters match.