Google Hangouts for mobile has gotten a major design overhaul. The design refresh comes as part of Hangouts 4.0, which is rolling out today on Android and was released about a month back on iOS. Hangouts 4.0 keeps the app's distinct green accent color, but it adds a floating compose button, cleans up and simplifies the interface, and presumably adds in all of the animated flourishes you'd expect from a Material Design app. Hangouts' Android Wear app should also be looking a bit nicer today.
In addition to the design changes, Google says that Hangouts 4.0 for Android should send messages faster and more reliably. The update also adds back in the ability to set custom status messages, and it's supposed to be less of a drain on battery.