So I tested and I'll give you my thoughts.
First, some concrete stuff. The green poison skull gas cloud things have a weird hitbox near the 'jaw', the lower left/right corners. Next, when using the golden phoenix's time slow ability, the green and red fire snake curvy bullet things also shrink. Which is to say that the trailing bullets don't slow down and rush up to the lead bullet's position, and hence appear to shrink.
And speaking of the golden phoenix. It's really OP. Its ability is way too convenient once you figure out the right distance to touch the screen. It's the only one I used after unlocking it (besides briefly testing out the new ones, of course). It kind of breaks the game, though I suppose it could be useful for beginners who don't feel like dodging everything. I also thought the green phoenix was the most useless. Pretty much every phoenix already has homing, and you can't even choose which enemy to kill first (more or less).
I'm not entirely sure what the briefcase is for, since I could just as easily click a stage and level up there.
To put it bluntly, the only thing that kept me playing was unlocking everything. After I unlocked the briefcase, I just stopped. Which probably means that I didn't find it all too interesting. A complaint that some people have about shmups in general is that it's 'all memorization'. Your game works on using bosses that continue to unleash the same bullet patterns, and then assorting a team of several bosses. On one hand, it means easily reusable code. On the other hand, that means it's scrambled eggs, sunny-side up, or boiled eggs every morning. Eggs, eggs, eggs; and only slightly different each time. Also, that I stopped immediately after unlocking everything means that aside from the unlocking, there was no other source of motivation to keep playing. More specifically, I didn't feel the need to perform well or put myself at risk in front of the bosses (or the other extreme, be really cautious), because I had infinite lives and there was no scoring mechanic. How well I played each individual stage had no effect on the outcome, like no extra soul drops or anything.
Or maybe I'm expecting too much from an android app?
I said before that the art is good but I'll revise my opinion. The art is really good. The sprites and animations are really nicely done. Though I didn't care for the music (medieval sounding stuff isn't really my type), I'd say it fit the aesthetics very nicely.
Overall, I was pretty impressed with the presentation, although the contents didn't hook me that much. I think some tweaks might be necessary. So good work and keep it up!
If you're still in want of random suggestions, I have one: A laser phoenix, or something that has piercing shots.
