Thank you so much for the detailed feedback. As the designer I can confirm that your vision of scalability is pretty align with mine. The idea of a permanent upgrade between staged is exactly what I want to do for a bigger version, much like kingdom rush series does.
What we have here is indeed a strong foundation, the boss and the upgrades were a quick way to show this potential but they are indeed lacking polish (short gam jams are hard hahaha)
Again, thank you so much for the feedback, we really appreciate it