You play David, an awfully small abstracted chosen hero tossed into a blissfully simple world overrun by giant culminations of evil physics-beasts. As David, you are given a slingshot-esque gift that you will have to use to conquer your colossus foes. Hold, aim, and fling to attack (Angry Birds style!).
Think Limbo + Shadow of the Colossus + Angry Birds.