This was an interesting mechanic. I feel like you end up in a flow state and everthing feels really good!
I wish there was some protection for accidentally clicking on the upgrade screen. I would be so focused on not being hit that i would accidentally click throuhg it quite a bit 😅.
Theres a really solid loop here and as you said you are going to continue working on it im excited to see where that will go! nice job, well done!