Thanks a lot for such a detailed comments. Yeah the sfx is not very good I have to admit. For the heart system, you are right about the demon(and thanks for noticing it!), it is kind of a reward for those who play this game more than once. Also the heart generates randomly in each room, so it is not based on if you lose one before or not. I'm curious what is the normal heart system you mentioned? And yes we were plan to have some ability to regenerate your health, but we didn't have time to add it...
About the random bouncing... yeah it is a bug. I haven't figured out how to fix that, might be some misconfiguration in the physics system. Also planned to have an ability to slow down/make heart stay longer, but no time to work on the whole ability system.
Agree with the mouse thing. the current input is more like a salute to The Binding of Isasc. Will consider changing it to mouse shoot if I'll keep developing it/make some similar games later.
Again thanks for playing it and leave such a good comment.