Great little game - well done Egor!
Good graphics and lots going on here - brill work for the Jam period.
Lovely music... ah, just seen it was Gruber (PS. You've misspelled his name on the game page!)
Unfortunately, I couldn't complete it due to (what I think is) a bug.
I went left, several times through the "repeating" bit, then went around the lake, got the key.
Then I died, but still had the key. Accidentally went up (back to where the door locks until you kill the bats), but then it used my key on THAT door! Now I don't have enough keys to progress. :o/
Anyways, congrats and all the best! :D