Auralux was an amazingly simple, fun, calm, yet addicting and difficult RTS game that was released back in 2012 and many players loved it. It takes Real Time Strategy like Starcraft and makes it as dead simple as possible, with little circles that emit units around them, and users have to use serious strategy to take over other worlds in the galaxy. It's hard to explain, but still one of my favorite casual games of all times.
Released in 2016 is a newer version, Auralux: Constellations. It's bigger, better, more exciting, and has support for multiplayer and Android TV. This is probably one of the most relaxing casual games you will ever play. There's something about the sound beating to the troops on the screen that's relaxing.
Check out this launch trailer video, then hit the download link below. You'll love it.