Missile Command-like. Click to launch a missile. Intercept the enemy missiles. They keep dropping until you are dead. See how long you can go!
You get 20 missiles to start, and they restock every 20 seconds. If your base gets hit, the missiles all explode in the launch tubes and can't be used. Thankfully, saftey regulations are very tight and no operators are harmed in the event of a base hit, but you must wait 20 seconds until you can shoot again.