Good submission! I had fun playing this. I agree there should be something to do that's a little more challenging for the player, since at the moment it feels as though the only interactivity comes from mining resources and buying upgrades, and I never felt like I was at risk of losing after spending so much on upgrades.
With some balancing this could be very fun. It's really interesting to see you put a resource collection minigame in a tower defense. Maybe a post-jam version? :D Thanks for submitting anyway!