The controls felt a little counterintuitive to me but I liked the intro. Overall a very good entry!

I liked the sprite/artwork, the movement was cool and the dash was fun.
Health regeneration was a little confusing/hard to tell what was going on. I noticed the large enemy helped with that. I was also a little confused about pressing F to enter the room/new section as I didn't understand what it was I was entering and made me wonder if I missed other routes/areas because of that.
I did feel that I kept getting softlocked near the end when entering a room with 3 levels not being able to jump 3 tiles high or get to the lower level, however I did manage to pride myself in beating the larger green enemy which was nice hidden touch.
But still super cool you managed to put it up/finished the jam in time as I found it hard myself to finish the game jam :) Good work!

The sprite work on this is very nice, as is the music. Really good aesthetics.

It would be nice to tell the player that they can double jump. It never occurred to me to try, and I got stuck for a while.

Is there any way to regain health? I'm not very good, and I keep having to restart from the beginning.

I absolutely love the way the slimes pop like a balloon full of paint. That's very satisfying.

Nice old-school sprites. Lovely color scheme.

I was really wishing for a fullscreen mode. I had a hard time seeing what was going on on that tiny viewport, and at one point I also encountered an enemy with a low contrast against the background.

Really liked how the enemies would explode into pixels when defeated, very satisfying. Same issues as the other commenters, I think save points would help a bunch, but I enjoyed it enough to give it a couple tries.

I really liked the art, music, and simple mechanics, but the playability made it really difficult for me. The screen size is too small and restarting the game everytime you die made me impossible to get further than the toxic water.

The art direction is quite endearing, though some design choices hinder the UX and readability of what's happening. 
Also, the screen size in the browser is quite small, I felt the need to zoom in to really play it. 

The controls are nice. But there's some clipping when jumping and doing the double jump felt like I wasn't properly in control, I ended up mashing the button more often than not.

like music, like graphic and overall this retro style :D Had problem with finding 'safe' path to this big green slime, but still had fun playing