Android is one of the most popular operating system for smartphones and Google is making it more efficient and better with the release of upgrades. Android has changed a lot since the release of cupcake version and Google is adding more features with every major release.
The evolution of Android from Cupcake to Kitkat is significant not only in terms of performance and features, but also in terms of visual appearance and design. The major change was from Gingerbread and Ice Cream Sandwich when Google introduced the Holo User Interface.
I saw the Kitkat upgrade on Nexus 5 and I found the Android 4.4 almost same as it was in Jelly Bean. The only visual change was in the launcher, the wallpapers and some system elements like notification bar and navigation bar. I found a very nice and clean concept for Android 5.0 on Behance designed by Codebuild.
I really liked the way the concept is done. The lockscreen is pretty much the same as we have in Jelly bean but with blurred background and 3-way unlock button. The lockscreen also displays the music player widget with album cover in case the music is playing the background.
The concept of swiping down with two fingers for more information like messages is pretty nice but not practical. The launcher concept is same but with clean interface and minimalistic icons.