I played this for a while, it's very good.
I would have liked if the progression was considerably faster, especially for a game jam. Sure this way I realised better what upgrades had what effect and thus could be more strategic than if I had gotten 6 new upgrades every round, but the latter is more satisfying...
I could probably have advanced quicker if I knew the "spawn copper" upgrade only became available after buying a stone pickaxe. I was like "Lets you mine copper"? That's useless, there is no copper! I'll buy that one when I see some copper appearing.
I liked how you could aim directly in one of the six straight directions to get the pickaxe to bounce basically indefinetely, having the unfortunate side effect that it creates a straight hole out of the center.
The visual effects on the things were really nice, like the copper one moving faster, making it all more visible what is doing what. I was never like "I have no idea how much of an effect this upgrade has". The lightning one could have been more subtle, and more clear from where it originated
I think it could have been nice if instead of the "wall bounce" being a chance, it just costed a certain number of ricochets, starting at like taking three quarters of what you have left. I don't know if it would work, but it would make bouncing straight into the void a bit less devastating.
The crates are cool, but I think they're a bit weak.
There could be a bigger incentive to try to stay alive longer, cuz for me the blocks just seemed to get stronger and thus getting less resources per point of damage. If there is already an incentive, I think it should be more clearly communicated.
I'm a bit curious why you decided to only use ingots, even for stone and diamond, when minecraft has some readily available textures for those.
I didn't expect the obsidian to spawn that quickly, but maybe I just bought the upgrade too late.
Nice game.