Gradius Advance, known in the United States and Japan as Gradius Galaxies (Japanese: グラディウスジェネレーション Hepburn: Guradiusu Jenerēshon, officially translated Gradius Generation), is a horizontally-scrolling shooter handheld video game developed by Mobile21 and published by Konami in 2001/2002. The game, released for the Game Boy Advance, is the only Gradius title available for the system. The game's plot is set between Gradius III: From Legend to Myth and Gradius Gaiden. Bacterion was developing a powerful weapon to use against the planet Gradius, but it was destroyed. A few years later it crashes on a planet and the planet gradually changes into a mechanical fortress, and the planet Gradius then sends the Vic Viper to stop it.
Source: Wikipedia, "Gradius Galaxies", available under the CC-BY-SA License.