Very nice entry, I enjoyed It a lot!
I'm a sucker for the 1-BIT graphics, accentuated with bright colors, so the visuals we're right up my alley.
The music is very nice and fitting. I can't recall the quality or amount of sound effects, so it's either good or fits with the game, but definitely not out of place.
Gameplay wise, it's nice, but personally, it's a bit fast paced, even "twitchy" for me. From the character movement, to the enemy attacks, everything is almost instantaneous. It's not that big of a problem with player controlled actions, cause' that's something you can get used to, but having no windup or tell on enemies is not great. Though there is a good variety in enemies, they feel more like a dynamic level hazard, then miniature challenges to overcome. The spider ambushes got old pretty quick, and there we're a lot of times where I just stood on the edge of a platform and mindlessly clicked on slimes, which really made me want to have some kind of autofire option or upgrade, to be honest.
I don't know how to feel about the upgrade system. I like it, personally, but grinding for upgrades feels a bit in opposition to the exploratory nature / design philosophy of the genre.
The map was interesting, filled with secrets and shortcuts, so it was fun to explore. Having the Rabbit Outpost act as a central hub and "quick travel" location was a smart decision.
I loved that the HP bar becomes transparent when the cursor hovers over, so you can see behind it. These little touches get a game from good to great IMHO.
Overall, great experience, spent way more time playing it then I thought I would!