U.N. Defense Force: Earth Joker is a vertical scrolling shoot 'em up game where you take control of one of four different pilots and their ships. Each with their own weapons patrons. In 2026 earth is attack and invaded by the powerful Slytow, with earths military unable to stop it. With Earth conquered and few survivors making it to Earths off world colonies all seems lost. But the thriving colonies are united under a new United Nations that have decided to take back Earth. After several failed attempts it’s now up to you.
As you make progress and fight of various flying crafts, tanks, and bosses power-ups come available. These can be collected from destroyed enemies and increase your firepower (P). There are also four types of support weapons. These are: front rockets (FRT), some kind of torpedoes that detonate on a set distance from your ship (ARD), homing missiles (HOM) side missiles (SIDE). If the fire button is held down for a certain duration of time the selected weapon charges and when released it creates a powerful burst attack. The game can be played solo or with a friend.