Solid game - simple and fun! I played all the way to the end, with maxed-out copper mines and gemstones. Ran into a few small bugs with buying upgrades but nothing game-breaking. Like @Typhoon said, I also really like the idea of getting random gem drops and it could be really fun and satisfying if you had a cool sound/vfx for these drops, or give the player more agency/skill in how often those drops happen. Really great work on your jam entry, and I'm excited to see what you do next!