I noticed that if you stay at the bottom of the level you won't get hit by any enemies spider will spawn, but are pretty easy to kill. Overall very interesting and fun game!! :)

You should add a double jump, or maybe a higher jumping power so people don't have to go through the portal to get to the 3rd floor. I did however enjoy the difficulty of the game :) By the way, the bullets pass through the wall if you shoot right next to the wall

The player character is too slow  :(

If you stay in the top right of the playing area, you can shoot to the left nearly indefinitely. For some reason the spiders can't hit you there. It was a very interesting game.