I was wondering where the key was and the moment I found it something suddenly zoomed through me and everything turned red, which did startle me. Luckily I did find the door again relatively quickly :D.
It seems some of the notes are duplicated though? I’m pretty sure I found some of the same notes in different locations.
I feel that some sound would make this game much scarier :P. If I heard something when the “thing” (whatever it was, it was too fast) zoomed by I would probably have actually jumped out of my chair!