Apple has built a complete, robust physics and particle engine for iOS 7. Elements don’t just go from point A to point B, they move through a “real” world. They react to the accelerometer and gyroscope, they collide and bounce off each other and with the edges of the display, and they can change color according to the environment around them. They behave like objects in space…
From Rene Ritchie’s excellent article at iMore on iOS 7
