The game are well made but that's all I can say.
I'd lying if I said the game was challenging because it's pretty easy for me since the boss doesn't have any complex attack pattern, but that's good if these are meant for the beginner bosses as a warm up.
*Who knows you plan to make a 5 or 6 bosses and trying to make easy ones to go first and harder ones for later but couldn't make it in time due to jam being only for a month.
I see lots of game trying really hard to put "Spin" theme on their games even it's looks nonsense, but in this game I barely felt the theme other than the second boss idle spinning animation I guess?
*Just saying, you probably can make a star shaped for bullets and made it spins when it moves, or maybe include spinning meteors, etc. to make a game felt the theme more.
I don't know if it's just me or are you intentionally made it that way but the window pop up for the first boss are covered by boss hp gauge while it's fine on second boss.
Also, it's definitely only me, I found building a tower of projectiles are more fun than fighting the bosses, I'm sorry for not enjoying your game properly and being an oddball.
That's all I guess, if I write something wrong or missed something, let me know.