It's slow for me too, but I assumed it was my old pc's fault.
Can you tell me what are your pc specs, pls?
I may have to release a windowed version. At 1280x720 it runs quite ok for me.
Oh, I had no idea it didn't work on linux, but I'm pretty sure I was still working with Ubuntu when I released it. Thank you for the heads up, I'll look into it!