Astro Invader is a fixed screen shoot 'em up. The player moves their laser base across the bottom of the screen and has to shoot down the aliens that appear above. What sets Astro Invader apart from other early shoot 'em ups is that the aliens, after being dropped from their mothership, position themselves in columns. Once a column is full the lowest alien drops down and suicide dives towards the player. As they hit the ground they explode and the player must make sure they are not within the blast radius. In addition to the standard aliens there are also UFOs that appear in the middle and to the sides of the screen. These must be shot down as they will kill the player when landing, no matter where the player is positioned. The game is over when all three lives are lost.