Ikaruga is a classic top-down style shooter game released in Arcades in 2001, and then subsequently ported to the GameCube, Dreamcast and Xbox Live Arcade systems. It was developed by Treasure Co LTD, and is considered to be a “spiritual sequel” to Treasure's previous shooter title Radiant Silvergun.

Like many other games in the shooter genre, the main goal of Ikaruga is to progress through levels, shooting enemies as they appear on screen and fighting large bosses. However, there is one main twist to the gameplay in Ikaruga: the “polarity system." Using this system, players can instantly switch the color of the ship from black to white, and vice versa. All enemy fire in the game is either white or black, and can be absorbed by flying through the bullets when the ship is of the same color. Similarly, opposing color fire kills you, but also causes double damage to enemies. This adds a layer of complexity to the gameplay, as you will need to be constantly switching polarity in order to successfully navigate through oceans of different color bullets. Same-color fire is absorbed into energy, which can be released as a mega attack that damages all surrounding enemies.