Galaga is the direct 1981 sequel to Namco's Galaxian.
Namco released Galaga in Japan in 1981, following Galaxian from 1979. The new game kept the fixed-screen shooting format but added more elaborate enemy formations, capture mechanics, and bonus stages. Players control a starfighter at the bottom of the screen while insect-like aliens attack from above.
A famous Galaga feature is the tractor beam. If an enemy captures the player's fighter, the player can rescue it; shooting the captured ship creates a double fighter with greater firepower. Galaga is therefore more than a graphical update of Galaxian, although both games belong to the same fixed-shooter lineage. The title is sometimes confused with Galaxian because both use alien formations, but Galaga is the later game and its official sequel.