Zalaga is a single-player action, shooter, casual, and arcade game in which players control a spaceship at the bottom of the screen, shooting at alien enemies that move in formations above. The core mechanics involve maneuvering the ship to avoid enemy fire while destroying waves of alien invaders. In this game, the setting is a sci-fi universe where players defend Earth from an alien invasion, with gameplay centered around shooting down enemy ships and avoiding their attacks in a fixed-screen environment. It stands out with its classic arcade style, simple yet challenging gameplay, and its faithful recreation of the popular Galaga-like experience, offering players a nostalgic yet engaging shoot 'em up challenge across various platforms including electron, Acorn Electron, BBC Micro, and BBC Microcomputer System.