The genius of Ikaruga's gameplay lies in its polarity system. There are two types of bullets, black and white. The player ship is able to shift between the two polarities with the press of a button.
Bullets of the same polarity as your ship do not cause damage to you. In fact, they help to charge a special homing laser. In Ikaruga, enemy bullets can be your friends.
PCGMedia's Tom reviews the PC port of classic shmup, Ikaruga.