Hmm my version naming for the demo must have been different from the full game. That demo must be old.
EDIT: Yep I checked, that demo is 5 years old.
The current version on itch.io (1.2.1) is the latest one, same on Steam. Do you have an old computer that can't run 64 bit?
EDIT 2: I have retrieved an older 1.0.6 version for Linux which should be more or less the same one as that demo and works with 32 bit Linux. I've uploaded it here.