First, an image of an example UI bug.  Those buttons are supposed to have text next to them. I was a...
I'm experiencing further issues. The game seems to be crash-happy, and quite often after any significant amount of play, the UI text will disappear. I'll gather pertinent information tomorrow.
Fixed; I uninstalled Steam, deleted the compatdata folder's contents, and reinstalled Steam, using steam --reset on both sides of the installation for the sake of caution. This appears to have worked.