Interesting, but not balanced all that well. I love the feel, presentation and sounds, but the core loop is has a couple of flaws. First, when you run out of shots, you have literally nothing to do but wait. It might have been interesting to add some sort of melee mechanic so you had something to do. Also, the enemies don't drop enough gold for the upgrades at first. So it takes a while to scrape together enough gold to buy extra bullets, more damage etc. I played until I had the max 4 shots, and a damage up. I was able to kill all the enemies with a single well placed shot, but then had to wait for them to beat up the chest to continue.
I couldn't see the point of making the 'tower' have more health. That would just slow the game down even further. The other upgrades made less sense too. And if I were to save enough to get the double gold, what is there to incentivise me to keep playing beyond that?
It's a wonderfully ambitious game to attempt in a Jam. It feels great, I love the excessive knockback on the shotgun. It's just challenging and engaging enough during combat. But the core loop doesn't work from a player's perspective.
I'm pretty sure there's a good game in there somewhere, just needs a little bit of tweaking to find it.