AngelRush is a top-down two-dimensional shooter, like Treasure's Ikaruga.

There are two colors of enemies and you can switch your polarity at any time to match them. Red bullets can't hurt you while you're red and likewise for blue. Instead, the player's ship absorbs the attacks which can later be unleashed in a special laser attack. In this way it becomes possible to survive even as the majority of the screen is covered in an unending stream of bullets. 

Much of the challenge of AngelRush comes from careful polarity-switching. This is especially true when fighting bosses, as they often fire bullets of both colors in overlapping patterns. The game also presents navigational challenges where the player must maneuver through continual streams of weapons fire, using their shields to absorb one color while avoiding the others.

The game use accelerometer to control the ship, swipe up to release homing lasers, swipe down to switch polarity.

AngelRush is truly a shooter fan's shooter.

Source: App Store