Kotlin is relatively new language developed by JetBrains, released at the beginning of 2015. It comes from the industry and is developed for the industry, it solves a lot of problems we are facing today, like null pointer exceptions. The language and all its features are working with JVM and are compatible and fully interoperable with Java 6, which makes it a great tool for Android development.
Before Android 5.0 Lollipop animations between activities weren't a strong point of Android apps. There weren't many ways to create a smooth and engaging experience for the user. A lot of apps looked the same when it comes to activity transitions. Fortunately Android 5.0 brought new Transitions API. It gives lots of new possibilities, not only activity transitions, but in this article I will focus on that area. Keep in mind, that Google doesn't provide backport library and there is no chance to do it on lower versions of Android.