Good Job! It's a great game!
Gameplay, visual, technically everything seems Ok!
There's doesn't seem to be anything wrong but if you do wish to hear my personal opinion:
Random Boss are fine, yeah I know you might set it that way so people won't get bored with same line up but for the first run or first encore, I suggested that there's a fixed boss line up because you include the upgrade and weapon here.
Some people might struggle with starting weapon if they faced a pretty challenging bosses, you made the bosses yourself so I'm sure you aware that all bosses are not equally hard, there are bosses that pretty easy especially with the right weapons while other can be pretty annoying.
Which is why I suggested to put easy bosses first to allow the player to grow in hope they can reach the last boss.
There are three bosses that I managed to get perfect bonus but that's only happened after or when I got the right weapon, also I kind of focused on one/two weapon I am familiar with so I have been upgrading only that and for some reason my weapon always stuck on LV3, idk is it bug or upper limit anyway I write this up based on my experience playing as Valerie and managed to reach encore 6, the last boss took my fav weapon so I was struggling on the first and second boss of that encore and loosing too much HP and yeah idk but the HP recovery after battle seems getting lower each encore or is it just me? I didn't keep track my HP because I'm too focused to look at the boss attack pattern after all.
I tried the other two but I'm not very good at using them, or rather I'm used with double jump for evade because it's versatile as you can chase moving bosses quickly or remain in the air longer to avoid danger on the ground while that's not the case for warp or double dash, oh well warp and double dash is just not my cup of tea that's it.
That's all I guess, if I write something wrong or missed something, let me know.
Also I'd love to hear your opinion about my game if you don't mind~