Not bad, its overall a fun game. There are a few clunky moments, but nothing that puts you off the game.
The graphics give off a quaint retro feel and the music seems fitting for the setting.
Control wise jumping is a bit floaty but easy to get used to. The biggest issue however is a lack of 'coyote time', this resulted in me often falling off ledges instead of jumping as you cant be even a frame late with the button press.
The game starts off very maze like at first as there are many blocked paths you don't have the upgrades for but starts to open up once you get a few upgrades.
Overall decent level design, but until I got double jump I kept feeling like I was slowly being boxed in as all the paths would end in a dead end in which I needed another upgrade. This left me feeling lost until I finally stumbled upon the upgrade. Afterwards however, the level design seemed to naturally lead me to the next upgrade and even the upgrade after that.
As for the ending, I'm not sure if I sequence broke as after getting the roll upgrade I teleported to the top then dropped back down to the small hole you fall past at the beginning. From there I shot a wood wall blocking my path and the mine began 'collapsing' requiring me to climb back up which triggered the ending.
finally a small bug: Not sure of the exact timing but I shot a wood wall as I jumped into it and continued to float midair as if clinging to the now non-existent wall. Wasn't hard to revert to normal by jumping.
also the bats kept just getting stuck on nothing.
Anyway, good work and thanks for the fun game.