Hello! I'm liking the demo. I think you nailed down a really nice ambiance with the music and art so far, and the hints of story have me hooked. A few suggestions:
The menu buttons were a bit confusing. It seems like "Bonus" and "Gallery" are yet to be unlocked, but it was hard to distinguish those buttons from the clickable "Start Demo" and "Continue" buttons. Maybe give the locked buttons some sort of lock icon type deal over them, or give the unlocked buttons more of a highlight.
At the beginning as you're walking up the path toward the house, if you walk beyond the top of the screen to the next scene the dialog will cut off before finishing. Either have the dialog continue or ensure the player can't make it there before the dialog ends.
Pausing didn't seem to have any effect beyond not letting me move around or interact. I paused during the chase scene and ended up dying. (Speaking of the chase scene, I loved the perspective on the hallways. It gave a nice claustrophobic and tense feeling.)
I've played through a number of times now, and it looks like my inventory persists across continues. I'm not sure if that's intentional. When I continue I start from right before choosing between the two Pendulums, and I have a Pendulum and a flower in my inventory already. It's also not clear weather the choice here is important. There doesn't seem to be any indication that anything changes between a playthrough with one Pendulum or the other. Although it is just a demo and it's impossible for me to say what is purposefully made unclear and what is just glossed over for brevity or mystery, I feel like if the Pendulum is part of the core gameplay there should be some indication of its effects.
It's a bit unclear what F and C do. I started to pick it up after a couple restarts, but it's not immediately obvious. Some more feedback to the player would be nice. For example, when teleporting, the glow around the feet is great, but I'd like to see some indication of what the power does before using it. Maybe a corresponding glow where the player teleports to? Maybe a sort of afterglow/shadow trail pulling the player to their destination? Teleporting seems like it will be part of the core puzzle mechanic, so letting the player know what to expect would be nice, especially since it doesn't look like you can teleport back.
I'm a bit confused about F being attack and teleport. It's a bit difficult for me to articulate why I don't like this. I think maybe it comes back to my last point about contextualizing your actions and giving the player confidence about what they are doing when they hit a key.
The animation when using F as an attack could be more indicative of what it's doing. It behaves like an attack, but the purple swirl doesn't quite have the punch that makes it obvious. I wasn't sure what I was actually doing to the door with the switch. I assume I'm breaking it down, but maybe I'm holding it open with magic? Objects should react to the magic. Maybe the door can glow purple before opening? Maybe the shadows can dissolve in purple light? Sorry I don't have a definite answer there.
I'm sort of obsessed with UX design, so that's kind of what I had the most feedback on: the little things that help immerse the player or take them out of the design. I hope I've made all my suggestions clear, but feel free to ask me any questions! I'm super interesting in where the story goes, so I'll be following your work.