0 Day Attack on Earth is a dual-stick shooter set in three cities (New York, Tokyo, and Paris) under attack by monstrous aliens. The player controls one of four aircraft types with varying characteristics in an attempt to cut through various minions to take down large bosses inside the level. Each city has seven levels or days, taking place in a different area of the city. The cities themselves are a combination of 3D buildings and 2D satellite map textures of the actual cities they represent. Up to four players can tackle the levels in online co-op. Any players less than four will be filled out by A.I.-controlled friendly craft. Weapon powerups can be collected by destroying enemy craft, and continued play will unlock new or upgraded playable ships out of a possible 40. Players can also fight each other online in a multiplayer versus mode.