Kotlin is an interesting language originally invented by JetBrains. Also you may be tempted to say that it's a "new" language it's in development for some time now and has already reached a decent level of maturity.
I've became interested in Kotlin when it was first officially announced by JetBrains a while ago. Unfortunately I haven't had much time to look into it. At the moment Kotlin gains more and more attention by developers.
With the recent announcement from Google to support Kotlin as a first-level language for Android development the visibility increased even more. I think that there is some hype at the moment but with a solid base.
Today I learned about Kotlin Koans that help you to learn the language by working through exercises in form of unit tests. This is a very nice and practical way to learn a new language. I will go through these exercises and commit my progress in a fork of the Kotlin Koans repository. Feel free to follow along.