Wow, very cool game! I didn't expect to see something like this considering jam only lasted 3 days, quite unique idea and I like it a lot, game looks nice and adding some sort of end goal would make it smth I would like to play in the free time. Though there are some problems, like the upgrade menu feels a bit overwhelming when you first open it and making tiles empty until you dig near them makes the world look a bit empty (maybe making undiscovered tiles completely balck would help) and a couple times game just froze for a few seconds and then all my progress was gone. But there will always be some issues when making a game in such a short period of time, good job, Great game!
Maybe you'd check out my game too ;)