Alien Storm is a side-scrolling beat 'em up game originally released in arcades by Sega in 1990, and later ported to the Sega Master System in 1992. The game is set in a futuristic world where an alien race has invaded Earth, and it is up to a special forces team known as the "Alien Busters" to stop them. The Master System version features two of the three playable characters from the arcade original: Garth (called Gordon in some versions) and the robot Scooter (called Slammer in the Master System version).
Alien Storm is a side-scrolling beat 'em up where players fight through waves of alien enemies across six missions. Each mission has players battling aliens on the streets and inside buildings, with the goal of rescuing civilians and destroying alien bases. The gameplay is similar to Sega's Golden Axe series, with the player using punches, kicks, and special attacks to defeat enemies. Each character has a unique energy-based weapon that can be used to attack enemies from a distance, and a powerful special attack that consumes energy but can clear the screen of enemies.
In addition to the side-scrolling action, some stages shift to a first-person shooting gallery perspective, where players must aim and shoot at aliens that pop out from various locations. These sections add variety to the gameplay and are reminiscent of the bonus stages in Sega's Shinobi games. The game also features a "running" section where the player character runs forward and shoots at enemies in a horizontal shooter style. Energy is used for special attacks and can be replenished by collecting energy capsules dropped by enemies.
Alien Storm is often compared to Golden Axe due to its similar gameplay style and Sega arcade roots. The Master System version, while graphically and sonically inferior to the arcade original and the Sega Genesis port, is still considered a solid conversion that captures the fast-paced action of the arcade game. It is remembered for its sci-fi theme, varied gameplay, and challenging difficulty. The game has been re-released on various compilations, including the Sega Mega Drive Ultimate Collection, cementing its place as a cult classic from Sega's 16-bit era.