Pretty fluid gameplay. It has some cheap feeling falling deaths- there's no real way to tell when you'll be falling into lava or whether a pit is bottomless and fatal. It's not the existence of the traps themselves, but rather the fact there's no telegraphing ahead of time to alert you of their existence. (My game had some balance issue in the first jam version too- hard to crunch and finish a product in that much time, let alone excessively polish, I know.) A little hazard indicator for pits, and removal of possible blind drops into lava would be really nice, I think.
For some next-version advice, I notice that the background kind of lags behind the hero and the camera jitters sometimes mid-jump. You can fix this by doing the process that affixes the background's X and Y to the player's position right AFTER his or her movements have been calculated (begin step?), as well as set the view's X and Y positions to align with the player then.
I don't think I have a problem with the sound effects on their own, but it is quite jarring to hear the overlapping noises of the charging enemies at the same time- it becomes loud with a few of them going. This could be alleviated if you ensure no more than one instance of the sound is going at once.
It was nice when the bouncy things were introduced; I felt that they added a nice dynamic to the gameplay. With a character who has a narrow repertoire of abilities like this blobby thing- or Jumper, for instance- I observe that the most successful mix-ups come from capitalizing on environmental mechanics like this, and experimenting with their possible synergy.
Did you ask Pixel or Brother Android for permission when utilizing their music? Although it's freely available that doesn't actually imply anything about its usage license. Although if he has granted you permission to use his tracks or has posted that they were open for usage, disregard me.
I'd echo the sentiment of the charging enemies in particular needing a bit too much to kill. When an enemy doesn't change its strategy often enough, or when it becomes more damaged, I feel that giving it an excessive amount of HP oftentimes feels redundant- with the charger enemies in particular, it doesn't seem like it proves much about the player to be able to hit them enough to destroy them. The only thing necessary is just to wait until their invincibility animation is over with and hit them again.
Any projectile enemies are a bit better in this regard- their HP is more significant in that situation, because then the player is tasked with deciding to try and burst them down in a short period of time or instead attack and retreat.
Ran fine on my comp but I do notice a lot of people with slowdown woes. Perhaps if you deactivate any unused instances (do you already?) outside of the large box that follows the view, things would work faster.
Anyway I like it and I think it's promising, thus the detailed comment! It's crazy that you finagled with GM's horrible room editor to make so many levels in such a short amount of time, haha. Nice job! :)