Hi Sub Atomic Quark, thanks for your reporting.
There was actually a setup problem in itch for the Linux version of the demo, please try again and let us know how it goes.
I got it to work after marking the binary as executable.
Which was in terminal as:
chmod +x cs_demo.x86
The game works but I got simulator sickness almost immediately when I got off the floor and rotated my character. I shut it down to prevent me from getting any more sick. The Unity 3-D default display and rendering routines are really sluggish which is where the simulator sickness (motion sickness in games) occurs. From what I saw before I felt sick, looks intriguing.