The story follows a rebel pilot named Shinra as he battles an enemy nation using a specially designed fighter called the Ikaruga which can flip between two polarities, black and white.

Titled "Project RS2", the game began as a sequel to Radiant Silvergun, and borrows many elements from it as well as the polarity mechanism from Treasure's Silhouette Mirage (1997).

However, this was found to be weak as it created too many breaks in the action so it was later added as an additional mode in home ports.

Treasure staff explained this was due to players expecting a more standard shooter offering but instead being greeted with a different game system that featured more puzzle-like elements rather than the twitch gameplay of bullet-dodging.

In 2002, Ikaruga was ported to the Dreamcast in Japan and began to grow a cult following from import gamers worldwide.

Most critics felt the unique game design choices were innovative, while some believed they stifled many of the classic shooter elements.

In retrospect, Ikaruga is regarded by critics as one of the best games ever made, especially in the shoot 'em up genre, and one of Treasure's greatest works.

The game features five stages, three levels of difficulty, and supports single-player or two-player cooperative modes.

[2]: 9 Ikaruga does not feature any pick-ups or power-ups, instead, the player can only rely on their standard firing weapon and a homing laser.

This energy emanated from an object she dug up from deep underground, which granted her unimaginable powers.

Shot down near a remote village, inhabited by elderly people who were exiled by the Horai's conquests, Shinra was rescued from the wreckage and was nursed back to health.

Hidden in a secret underground bunker and launched via the transportation device called "The Sword of Acala", Ikaruga is the first fighter to be built with both energy polarities, and is capable of successfully switching between the two.

Shinra releases the Ikaruga's restraint device and unleashes a massive attack to destroy the object for good, sacrificing himself in the process as the ship overheats and explodes.

Kagari's fate at the end of the game is the same as Shinra's, dying as her ship is destroyed in the final attack against the object.

[3][4] Since company resources were allocated for Sin and Punishment, director Hiroshi Iuchi worked on Ikaruga at home on his spare time and developed a prototype with help from programmer Atsutomo Nakagawa.

[3] Originally, Radiant Silvergun was intended to be a trilogy, and Ikaruga began development as a direct sequel, codenamed "Project RS-2".

In the beginning, the stages were designed with the combo system in mind, however this made the optimal route too obvious.

[11] Although not yet published in the West, Ikaruga began to garner a cult following in North America among import gamers.

On August 15, 2002, it was announced that Infogrames' Japanese division had picked up the publishing rights to a GameCube version of the game and would release the title in January 2003 under the Atari brand name.

[13][14] Initially, Infogrames' North American and European divisions had no plans to release the title nationwide, but on January 28, 2003, it was announced that Infogrames would publish the GameCube version in those territories as well, with representatives at the publisher citing the popularity of the title in Japan and a growing fan base around the world.

[15][16][17] The game was released in North America on April 15,[18] and in Europe on May 9,[19] branded under the Atari label as in Japan.

[20] It was released on 9 April 2008, and included new features such as leaderboards, achievements, and the ability to record and replay playthroughs.

They both felt Ikaruga was a brand new type of shooter and that bringing variety was important to the growth of game centers.

[34] The visuals, art design, and sound were universally praised and some criticism was directed towards the game's short length.

[1][32] The difficulty was both highlighted for being inviting to old-school shooter fans, but was also criticized for building a barrier to genre newcomers.

[39][40] Topher Cantler of Destructoid gave Ikaruga a perfect score and dubbed it a "work of art".

[49] Adam Smith of Rock, Paper, Shotgun called Ikaruga one of Treasure's greatest works and "one of the most perfect games [he] ever played.