Your game was one of the first I tried because I remember it from all the updates you've posted. I like the rat boss and the wall of rats.
Since the shop fills a progress bar, many times I found myself forgetting to check it and upgrade. The white reflection on it does help, but for me it was not enough. I was wondering if the skeleton could give us a sign, maybe wave (or dance, ok maybe dancing is too much).
Even if he just woke up and said "heh heh" it would be a good reminder and increase their participation (they have charisma).
A thing I really enjoyed and your game brings to the "survivors" table is the fact that the landscape moves instead of the player moving. This opens a few new possibilities, like immobile enemies showing up and leaving the screen (Shmups did that a lot). Big dragons and catapults come to mind.
Just my overall feedback. You got a nice game going. (Rat character maybe?)