You did a great job building atmosphere, which is just about the most important and difficult thing you can do in a horror game (in my opinion), especially under a game jam's time crunch. The scenes with the monster in the window and seeing its shadow were both well done.
The best way to improve this would be to have more payoff for all the atmosphere you've built up, though. I'm surprised that nothing tried to chase or kill me in this game. It ended sort of anti-climactically right after the scariest part, which would've been the best part to really scare the player. You worked hard to build that atmosphere up, so take your reward and scare me with it!
All that said, I love a good horror experience. Great job, I hope to see more from you guys in the future.