I also thought about integer overflow while braintorming, but eventually we chose another direction, it's cool to see that someone followed this path ! The deckbuilding aspect is cool, but I feel like the cards' text is a bit hard to read. I was confused about the black squares until I read the description, that's on me for not reading it :P
Overall it's very satisfying to see a gigantic amount of droplets hit the target !
Nice job !