Since my last response, I have tried to run Sunbeam on my own Linux (Kubuntu 17.10) laptop, which is also an i5 system with integrated graphics. It objected that there were a bunch of 32-bit libraries missing. After resolving that by pulling copies of those libraries from another Kubuntu 17.10 machine, it then crashed on launch with the message "process exited with code 1". I suppose it could be a video driver issue - your friend and I may not be using the same Intel driver (or i5 CPU for that matter). Another oddity I spotted in the cave *.txt file was that it listed 4 CPU cores, although my laptop's i5 is supposedly a dual core.
Okay. The graphics are now ok on my first machine sfter running some regular system updates and updating itch. I don't know what did the trick.?????
Huh, how weird. Well, I'm really glad you managed to resolve the problems, even if it is a mystery as to what caused them in the first place. I'm sorry you had to go through all that though. I hope you enjoy the game enough that it was worth it! At the very least you know you should be able to run other games made with Unity without the same issues.