Wow! This is practically a feature-complete roguelite-type shoot em up. You've got pretty much everything: there's stages with different rewards, there are multiple upgradeable stats and a sort of currency to boost them even further, and an endgame boss. I like the use of the rooms to branch out progression in different ways based on how the player is performing. Visually everything is tied together nicely, the sprites and icons are nice and the UI makes total sense as far as what the upgrades are improving for the player.
I hope you can build on this and make a gameplay loop out of it - it's easily something that can be expanded into something more than a linear path to the end boss. For constructive feedback, I think having some more varied enemy attacks that are signalled properly might add a bit of variety, particularly to the boss, and this could provide the context to repeat the gameplay loop and up the challenge factor.
Great work!