Ikaruga (?, lit. Japanese Grosbeak) is a shoot 'em up video game developed by Treasure. It was released in the arcades in 2001 on the Sega NAOMI, subsequently released on Dreamcast in Japan and then worldwide to the Nintendo GameCube, and was released on Xbox Live Arcade on April 9, 2008. It is a spiritual sequel to Radiant Silvergun.
Ikaruga's gameplay centers primarily around the polarity mechanic. Only bullets of an opposite polarity can kill the player. Same-color bullets are absorbed and converted into energy for the game's special weapon, a homing laser. Switching the ship's polarity also changes the color of the ship's bullets, and shooting an enemy using opposite-polarity bullets will cause double damage. Thus, much of the challenge of Ikaruga comes from careful polarity-switching, choosing between high damage and (relative) invulnerability. Ikaruga was well received by critics.
I love shooters. But you want to see a REALLY HARD GAME check this one out! This is what a space shooter would be like in real life when your tiny ship faces off against a massive final boss.