Nemesis is a horizontal scrolling shoot 'em up arcade game released by Konami in 1985. It is the first game in the Gradius series, and is known for introducing the weapon selection system, where the player can collect power-ups and activate them in a desired order. The game follows the Vic Viper spaceship, which must destroy the alien fortress Xaerous and its leader, the Bacterian Emperor. The game features seven stages, each with a boss at the end, and various weapons and power-ups to collect.