I think it would be cool to have a bit more easing into the game. For example, some Key indicators on the healing icon would be useful, stuff like that.
I liked how mutation was implemented into the game, by having it be a bit random, although at times it felt a bit frustrating. But I think that was intended! It was a nice touch that the mutations have upsides and downsides, which fits in pretty well with the idea of mutations being unstable.
At times it felt like the game was a bit too unforgiving. The enemies feel a bit too tanky and they deal a bit too much damage.
I really enjoyed the aesthetics!
In terms of sound, the death sound sometimes plays way too loud. The first time I died I got kind of startled lol!
Overall, pretty cool game! With a bit of polish it could be even better, keep up the good work!