It took hard work and cunning to make a game this boring! You have a right to be proud!
I played until I reached the stone wall at 200 ft. I decided to try going around the top of the wall. That took a while, but after discovering it's not possible to go around the top, I'm giving up.
I timed how long it took for a single mining trip while in the middle of digging that tunnel around the top of the wall. Breakdown:
75 seconds to get to where I finished previously
110 seconds to mine
85 seconds to get back to the base
15 seconds to recharge
That's a total of 285 seconds for one mining trip, out of which less than half (110) seconds were spent actually mining. That was with 4/4 engine upgrade, 3/5 drill upgrade, 4/7 battery upgrade, and 2/7 recharge cells.