So addictive! So fluid! Not to mention very cute and funny. I was smiling the whole time.
The music contributed so much to the tone. Absolutely loved it. The marimba (I think that's what it is) is so funny. Gives me Crash Bandicoot vibes, which is perfect.
The movement feels great. I love that you can move at full speed while attacking. Not needing come to a stop to attack really makes the flow feel good.
And I want to mention the big smile I had on my face when I realized that the jump has a hitbox. It's not only hilarious, but actually contributes to the great flow because you can jump into and hit enemies that are above you without slowing down. And I can imagine somebody giggling to themselves as they thought to put that hitbox above the jump sprite. Just such a great (and funny) touch to character controls. I love that kind of attention to detail.
On the flipside, I want to bring up the opposite situation, essentially. There's no way to place a hitbox below you (at least as far as I could tell). Which leads to some awkward situations which feel like they break up the flow such as this:
Basically, I have no way of hitting this enemy besides jumping over it, turning around, and then hitting it. I wanted to be able to hit it from above so bad!
Not being able to put a hitbox below you also makes some segments where you fall a large distance into an area with enemies feel essentially random whether you get hit or not. You may land on an enemy or you may not. The double jump does help since you can double jump at any point in the air so long as you haven't used it, so you can stall your landing before hitting the ground, but I think being able to have some kind of downward attack could really add a lot.
There's straightforward ways of doing this. Such as making it so Cirno can jump on top of enemies to hit them like Mario. Or giving her a downward attack when the player hold down/down in the air. But maybe these kinds of things were considered and dropped due to game jam time limits or something else.
Regardless, that's a relatively small gripe, and overall I loved it!