OMG, I wonder how much time you've been playing to actually have negative amounts. The label is capturing the mouse input so you cannot click behind. This is a bug I found when I broke the game too.
Being honest, I don't know whether fix this bug or rebuild it from scratch.
Viewing post in Rogue of the sea jam comments
i actually didn't play that long, I just found a really good strategy where I would upgrade mostly the amount of supplies I get and then once I could get like 300 supplies just on the first level i would go around the perimeter until I found the next stage, and travel the perimeter over and over until i got to a super far stage that gave me a ton of coins
the amount the prices go up does not correspond to the amount of gold you can get which meant it got to a point where i could raid like one city and have enough gold to buy like 20 upgrades