Incredible work!
This is a quick and understandable gameplay loop that steadily gets more difficult over time. It's satisfying to sweep your mouse over the enemies you were just being so delicate around, and it really makes you focus to dodge foes at later stages. It's fun, simply put.
Not only is it fun though. It's clear that you put a lot of attention towards player feeling and feedback. Each time you are hit, the damage sound effect pitching down is a way for players to instantly know around how much health they have. Each time your mutation finishes, there's a grace period where you can't be hurt. When the player is wildly flinging their mouse around, they're bound to mistime their mutation, and you anticipated that.
Simple and short, but incredibly well done... And as a solo-dev?! Way to go!
No doubt in my mind this is one of the winners.