It's fun but slowing down while shooting feels a little counter-intuitive to the run-and-gun gameplay, and at the start enemies took so long to kill I was tempted to just jump over them until I realised you'd get occasional upgrades.
It's hard to really feel like there's a lot of skill involved, since a lot of the beginning is really just waiting for enemies to die. Personally I'd enjoy a melee attack or parry, and maybe strafing.
Platforms kind of 'snap' to you, so a short hop will still end up with your momentum being shifted so you end on top of the platform anyway. The level design doesn't really complement this, with enemies on a platform you have to kill yet avoid at the same time but can't jump else you end up on top the platform.
The fact that your movement speed can change and you can have a differing amount of jumps doesn't really play too nicely with the bullet hell format enemies have later on - you end up misreading how far you'll go if you tap a direction because it'll change depending on your upgrades.
The boss fight is a funny fakeout and plays nicely with the controls, but I feel like there's some annoyances like the boss absorbing your bullets while enemies across the screen are shooting at you, and it being very difficult to dodge and attack at the same time due to a lack of strafing
I wasn't able to beat the boss, but what I played was fun - I just feel like it could be better