I think I've encountered an issue. I can't click anything on anything. Nothing is getting highlighted either. I'm on Linux by the way.
could you document your issue on video? Also, try using various display modes - fullscreen, windowed, and different resolutions. I've seen Unity UI get confused on stretched modes, for example.
Note though, that I haven't really tested the game on Linux, but so far nobody had reported any issues to me, so perhaps it varies from distro to distro.