The healing is so little, and combined with me sucking at bullet hell and not knowing what Gura's hitbox is... there's a hole in my wall now and desk kun has maybe a generous sliver of .5 hp left. So, let's go in depth...
Please don't interpret me as a hater or anything, I actually enjoyed everything for the most part, I just want to get the criticism done first. I just... don't often rage quit things, but the Cyber Hunter boss brought me to that point. After multiple attempts, a hole in the wall, a nearly bruised hand, and a fear of hurting anything else, I called a very angry quits.
Some suggestions would be either buffed healing or more fish during certain bosses, a dash feature to allow for evasion when needed, maybe an option to show Gura's hitbox, even if it's just a practice mode? And finally, the special pickups could do to spawn a bit more frequently, 2-3 times per stage instead of 1-2. Especially when that's the only thing that can reliably damage late game bosses.
I said I wasn't a hater, so now it's time to prove it. There's actually a lot that I love about the game. Firstly, the controls are tight and responsive, which means that most deaths don't feel like something cheap and/or out of player control. It also makes winning stages feel earned when they're particularly difficult. It adds a sense of accomplishment, which may be a weird feeling to get from just a control set-up, but it's present nevertheless. Secondly, the visuals are amazing. Whenever I've played or seen bullet hell games before, it's always a layout with the playable character starting from the bottom and being able to work their way up the screen, a la Touhou, so it took a bit of getting used to doing a side-scrolling style for this type of game, but the thing that managed to pull me through that is the impressive visuals. Everything has a very unique look that helps distinguish to which part of the screen one would want to go. It helps that this also allows for more dynamic backgrounds that were always a gem to look at. Thirdly, the audio design is God Tier. I haven't had this big of an audio rush with any kind of bullet hell experience since the always-satisfying sound of the Master Spark. Defeating a boss and hearing the stage's enemies and threats around you die out with it is music to my ears. The audio clips were always very fun to hear, helped by the fact that they're crisp and easily recognizable. I also got a chuckle whenever I made a complaint out loud and it was subsequently repeated by Gura. It made the experience much more enjoyable.
Overall, I'd give the game a 4 out of 5 stars. The criticisms of the gameplay are the only hinderance, but I'm not going to rule out that it might just be me being trash at the game (and bullet hell in general). However, for the most part, the gameplay is seamless and extremely fun, the audio and visuals are amazing, and the game overall is just a very impressive masterpiece!