0AD HiDPI configuration
I'm a fan of RTS games and 0AD has been one of those games that I wanted to try for a couple of years now, so I installed it on my new laptop, a Dell XPS 13 with a 4K (retina) display. The game works like a charm, of course, but the GUI is not configured by default to work on a HiDPI screen.
I was googling a bit and came to a thread in the forums, posted a few days ago, and found out that there's an option that scales the game. Add this line to your
gui.scale = "2.0"
If you don't know where this file is, look at this page. There's info for Windows, Linux and OS X.
Go on a try it, the GUI looks a bit pixelated, but nothing really annoying.