I've been using Duolingo for over two years to learn Spanish and, more recently, French, and this app's capabilities are almost magical. But Duolingo is getting even better with the introduction of bots. And this changes everything.
I don't normally talk up self-up topics, but one of the things I'm really passionate about is learning. And while my focus has shifted over time, I make a point to set time aside each day to learn ... something. Part of this effort has been directed at maintaining my software development skills, and I've spent much time over the past several years learning the basics of iOS programming and, more recently, trying to complete an Android Basics Nanodegree at Udacity. (I'm 44 percent done as I write this.)