It was a good game with a good concept. Regardless, I'd like to offer some tiny criticism.
To get straight to the point, the base form of IT is the creepiest. No doubt. And while I know IT takes the form of others as this is just the movie, 'IT FOLLOWS', in indie game form, the other forms are just more goofy than creepy to me. IT should just stay in its base form the entire time so I have no reason to crack up at its goofy 'mimic' appearance again.
Also, the 'creepy SFX' that plays when you have a direct line of sight of IT NEEDS to go in my opinion. ITs already a pretty tall entity, making IT easy to point out, so the SFX is just unnecessary to me. But that's not what bothers me. It's the realization that this game can be a whole lot scarier without it. Combine that with how tall IT is, you're guaranteed to not get caught by IT unless you get stuck in the crowd or run out of stamina. Also, consider making him the same height as everyone else. Force the player to actually have some situational awareness and look around for IT.
Finally, maybe add a tiny story that can answer unanswered questions. Like the point of the briefcase and why it is so important. Unless that's something that is answered when you're caught, but I didn't get caught.
Anyway, that's it. I just wanted to add some constructive criticism as I do think the concept is scary and could make for a great horror game. Good luck in your future game developer endeavors!
Much love!
P.S. Just read that this is your first attempt at making a horror game. Sorry if I came off as an a-hole. I hope you decide to return to this at some point!