Ikaruga's gameplay centers around the polarity mechanic. Only bullets of the opposite polarity can destroy the player ship. Same polarity bullets can be absorbed by the player's ship and be converted into energy for the ship special weapon, a homing beam launcher. Switching the ship's polarity changes the color of the ship's bullets and enemies of the opposite polarity with suffer double the damage with your bullets if hit with them. Thus, much of the challenge of Ikaruga comes from careful polarity switching, having to choose between high damage to the enemies or (relative) invulnerability. This becomes esspecially true during boss fights as they fire bullets of the two polaritys in overlapping pattens. The game also presents navigational challenges where the player is forced to fly through a continuing stream of weapon fire where the player can absorb one color and avoid the other. Ikaruga is not an easy game, but think of it more as a thinking man's SHMUP!