is a fixed screen shoot 'em up that is almost identical to Galaga
. The player controls his space ship along the bottom of the screen and has to shoot at the aliens that move around above him. The enemies fly in formations and will either try to shoot or collide with the player's ship. Once all of the aliens have been killed the player moves on to the next level. After every few levels there is a challenge stage where the enemies fly past in a certain pattern and the player has to shoot down as many as possible. Some ships can trap the player's ship with a tractor beam. The player can then recapture it by destroying the ship that captured it and thereby get two ships at once with twice the fire power.
Zalaga can be played by one or two players with either keyboard or joystick. An operator mode allows the player to customize some of the settings, such as start screen, automatic fire and reload speed.