UPDATE!
I have made a lot of progress in the game, and I must applaud you for having such a big demo available to play for free. There were several nitpicky things I could mention, but I'm only going to bring up the things that are really bugging me.
If you try to fire the gun right after moving, it points it straight up and doesn't fire.
Why am I being attacked by books? I don't know why the books keep dealing 2 clicks of damage, I'm assuming it's intentionally hard to avoid, but a little warning would be nice.
More importantly, I made it to the area with the spikes and the skeleton guy I'm supposed to grapple onto with another blue thing after it. Whenever I grapple the skeleton guy, I get stuck in the ceiling, which not only softlocks me if I parry the skeleton, but also makes it so I can't progress. I tried it several times and it keeps happening. (EDIT: Okay, I figured out you're supposed to shoot the skeleton and then continue. Still an easy glitch to pull off though.)
Great job on the game though, it's really quite fun!