Oh thank god you added checkpoints later on, I was so close to throwing my laptop out the window...in other words you succeeded at making an annoyingly hard game ;). I like that despite a simple art style the game-play is so good and immersive, you just forget about anything else. Maybe one thing I would suggest is to make the music file longer. You had a pretty short song that, when looped, quickly became annoying. On the other hand annoyance is the core of the game like that so maybe it's good?
Overall, I like your project! I would also appreciate if you would rate mine :)