I gave myself about an hour or 2 to just add some small things like that because I feel it drastically improves the game. The enemies slowing down was actually originally a bug feature where the enemy would stop while the iframes (they aren't actually invincible, but the player is when the player is in iframes) were going on, so I decided to add it. The player's jump was just something I ended up getting used to, its buggy lol. I intend to make it feel better (and not make you able to just stay on the ceiling for about a second. The way that the hit detection works is actually not separate hitboxes, because I don't know how to do that, so it just checks if you are going down.
Thanks for the feedback, I do intend to keep working on this game.