U.F.O.

U.F.O. is a fixed screen shoot 'em up that is based on the arcade game Astro Invader. Rampaging hordes of kamikaze aliens are attacking the earth and of course it's up to the player to shoot them down before they crash into the surface. What sets Astro Invaders variants apart from other shoot 'em ups is that the aliens position themselves in columns after entering the screen. As the columns fill up with aliens, they begin to descend until they explode upon hitting the ground. If in range of the explosion, the player will die. In addition to these normal aliens, there are neutron bombers whose explosion range covers the full screen and therefore has to be shot down. The player has three lives.

Source: TheGamesDB