You are correct indeed! I assume then you are not on Windows, probably Linux then. Unfortunately, the game doesn't support an other OS than Windows at the time (even if I see a not-so-complicated path to run on Linux). I can see other areas of the game where I use DirectX only APIs or Windows APIs.
It is still a pre-alpha game and I'm looking to validate if there is a real interest for it. So I cut a lot of corners to have a playable prototype. You are the first to ask for a Linux version (still assuming you are on Linux). When it will be an obvious obstacle to more potential players, I'll work on it!