Thank you for this great looking development! I like the mining mechanic, and I'm eager to see the final product. I know you're already working on your own ideas, but here are some more:
-A metal detector or similar item that blinks or beeps faster and faster when you dig nearer to gold, and maybe changes color or tone when you get close to a hazard block (I presume those will exist in the final release).
-Some other interesting use for the Dark Gold Ore besides paying off the Blacksmith or selling it for pennies. I'm thinking of some alchemical application: perhaps enough Gold Ore could cure a resin-enhanced wand so that you can add more upgrades to it without losing the resin bonuses, or fix an enchantment on another item so that additional upgrades don't eliminate the enchantment.
-Instead of a solid edge that you can't mine through, have the edge be some kind of hazard. For instance: a player mines too far, and then water breaks out and washes the player back toward the center (and are those piranhas?!); or perhaps mining too far just drops the player plummeting into the next level for fall damage.