Fun little game! I thought the shadowy art was really cool and definitely game a spookie theme to the game.
If you wanted to improve I suggest making the lower level brighter so the player can get a hold of the controls and what is going on. I found myself shooting just so the bullets could show me what I was walking towards. I also suggest making the stairways clearer, I was confused that I had to hold jump on them to ascend.
Overall a great start with a lot of promise!