iOS 7 introduced major design changes including a flat user interface, parallax and motion effects, transparency, and new icon grid layout. It also included engineering improvements like new frameworks for games and networking, enhancements to existing frameworks, Xcode 5 updates, and full support for 64-bit processors. While the redesign was controversial, adoption of iOS 7 has been rapid with over 74% of iOS devices now running the new operating system just a few months after its release.