With Android 5.0 Google added tons of animations and effects to the interface to make things smooth, fluid, and more lively. However, Android 5.1 added even more. They're small changes, but nice little touches that everyone can enjoy.
Tapping WiFi, Bluetooth, or most noticeable, the auto rotate button, you'll see nice little visual animations that the setting has been selected. Again, nice little changes. These same animations can be found throughout the Clock app for alarms, timers, and more. It's the little things!