Bangai-O

Bangai-O is a 2D side-scrolling multidirectional shooter. The player controls a weaponized mech that is piloted by the two main characters, Riki and his sister Mami. The story follows Riki and Mami in their efforts to stop criminals from smuggling fruit contraband to finance their evil deeds. The player can fly freely around each of the game's 44 stages, and must find and destroy the boss in each stage to advance.

The mech can shoot in eight directions, and the type of ammo is dependent on which character is piloting. The two pilots can be interchanged instantaneously, Riki fires homing missiles and Mami shoots reflecting projectiles which bounce off walls. The stages are populated with destroyable buildings and obstacles, as well as some walls that are opened by switches. There are also hazards such as gun turrets and enemy mechs which fire projectiles at the player.

The idea for Bangai-O came from Treasure employee Mitsuru Yaida (commonly known by the pseudonym "Yaiman"). He remembered playing an older shooting game that amazed him with the sheer number of bullets that could be rendered on the screen at once. Even though Yaiman and other staff behind the game have not identified the game, industry analysts agree that the game is almost certainly Hover Attack (1984) for Japanese computers. Yaiman began thinking about the programming challenges involved in detecting when the bullets collide with other objects, and started work on a prototype.

He later received permission from company president Masato Maegawa to pull in other staff and work towards producing a full game. Yaiman served as the main programmer and "General Manager". About ten people worked on Bangai-O.

Bangai-O received positive reviews for its initial Nintendo 64 release. Critics enjoyed the manic and unique gameplay that they believed was characteristic of Treasure's video games. Most compared it to older shoot 'em ups and action games. Eric Mylonas of GameFan called it a mix between the free-floating gameplay of Sub-Terrania (1994) and the rotating shooting action of Omega Boost (1999).

He appreciated it as one of the few shooters on the Nintendo 64, and compared its aesthetic missile shooting style to Macross. an addictive and original hodgepodge of genres and game mechanics that defy easy explanation". Journalists commended the variety in the game's design that kept it feeling fresh throughout. Anoop Gantayat (IGN) wrote that the level design made good use of each character's shooting mode.

Bangai-O received two sequels. The first, Bangai-O Spirits, was released for the Nintendo DS in 2008, and the second, Bangai-O HD: Missile Fury, was released exclusively on the Xbox 360 via Xbox Live Arcade in 2011. The games feature most of the same core gameplay ideas as the first game, but evolve on them with more weapons and gameplay elements. Both games included level editors, and the latter features multiplayer modes.

In February 2026, two independent groups released separate fan translations of the Nintendo 64 version. Both feature original translations not based on that of the Dreamcast version.