[1] In each installment, there is a threat to humanity posed by the invasion of Earth by an alien lifeform known as the Crystals.
In the wake of the Crystal proliferation, the world joined to form the VCD, which must launch a counter-attack with their powerful weapon based on Crystal technology, the Fighting Thunder attack craft, for the future of humanity.
The first three Raiden games were published by Seibu Kaihatsu and distributed by Fabtek (US), The Metrotainment Network (Asia), and Tuning Electronic (Germany).
Viper Phase 1, released in May 1995, has an exhaustible secondary weapon system (indicated by a bar meter).
An updated version of Viper Phase 1, released three months later, modified the weapons system to be similar to the Raiden games.