Geo Storm was released in September 1994 in Japan.
The game was originaly an order from the USA, Gun Force had a nice success in the US, so a sequel would be a great idea. It's why it is known in US as "Gun Force II
The development was chaotic since Irem closes its doors (March 1994) before the release of the game.
During development, this game was code named 'A2'. The name Geo Storm came from the name of the game designer's sport car of these days; the Isuzu's Geo Storm.
Some musics in this game are directly recycled (and remixed) from "Air Duel
", another Irem game from 1990.
The Stage 1 music is a remixed version of the Stage 4 music of "Air Duel
The Stage 2 part 1 music is a remixed version of the Stage 1 music of "Air Duel
The Stage 2 part 2 music is a remixed version of the Stage 3 music of "Air Duel
The voices of the female prisoneers were done by the sound designer itself, Hiya!, then re-worked on the computer.