Vertical shoot-em-up ported from the Naomi Arcade version. Ikaruga is more or less a sequel to Radiant Silvergun by Treasure, on the Sega Saturn.
Based on a two-colors system, the player has to switch between the black & white sides of his ship during gameplay.
The black side is immune to black enemy bullets which it consider as bonus, and dies on impact with a white enemy bullets. Your own black bullets damages white enemies twice as more as white bullets. And vice-versa for the white side. Those properties makes a balance between protecting yourself well and killing enemies fast.
This aspect, combined with specific enemy patterns and a combo system makes Ikaruga an original shoot-em-up with a dose of strategy.
In Japan the Ikaruga Appreciate DVD was released in 2003. It contains replays of full games played by three of the world top Ikaruga players of the time completing levels with unbroken chain combos. Scores are 32,178,600 in easy mode, 35,759,960 in normal mode, and 34,289,970 in hard mode.