Alien Outbreak 2: Invasion is a top down shooter where you will battle waves of enemies and use the power-ups they drop to aid yourself. Your movement allowance via mouse is horizontal and vertical to three quarters of the playing field. The power-ups are offensive or defensive in that you will get upgrades to weapons, secondary missile or explosive weapons and you will get shields and invisibility spheres. There are thirty two different types of enemy fighter vessels and eight different super-boss enemy garrisons. The enemies attack through nine waves with the tenth wave reserved for the boss battles. Enemy tactics include random shooting, homed projectiles and mines. The garrisons, naturally, can release fighter ships to aid in their attack.

Protorions, or alien ghosts, who are determined to wipe out the Galarion system, have possessed the friendly races of Humans: Tekkos, Kzeos and Insoids, and have only one thing in their way. A small ship armed to the teeth and piloted by you. Through eight missions and eighty levels of space shooting mayhem you will have to prove your courage and defeat the alien bosses.