The keys and NPCs stay in the same place. Non-dynamic terrain and permits also don't move. The top 2 layers are always completely covered in dirt. Other than that, the dynamic terrain is randomly generated. However there are no valuable ores near the top.
Basics: Dig, get permits, and save the mayor (Cole).
Health = How much damage do you have to deal to the ore/rock to break it enough for you to collect?
2 Health
5 Health
10 Health
50 Health
100 Health
300 Health
500 Health
1500 Health
There are large red barriers blocking you from saving the mayor. To remove them, you need to buy permits from The Broker. There are 8 permits, each corresponding to one ore. The cost of each permit is 5 of the corresponding ore. Each permit removes 1 barrier. Permit 1 is the lowest and is dirt, while Permit 8 is diamond and is the highest.
Common Pickaxe - Free - Deals 1 damage per hit
Uncommon Pickaxe - Costs 10 Dirt - Deals 5 damage per hit
Rare Pickaxe - Costs 10 Stone - Deals 25 damage per hit
Epic Pickaxe - Costs 10 Silver - Deals 100 damage per hit
Legendary Pickaxe - Costs 5 Ruby - Deals 300 damage per hit
Upgraded pickaxes are not necessary but make it a lot easier to mine.
I usually group the ores into five categories:
Dirt
Sand and Stone
Copper and Silver
Gold and Ruby
Diamond
Between each category I go up and buy permits and pickaxes. The three items I hold are dirt plus the two ores. After that, mine the first two layers until you get 150 dirt, then build so it is easy to jump from one platform to the next (1), and then once you run out of dirt then mine the column (2). You will end up with an easy-to-climb structure like in (3).
This is how to build the tower.
This is the dirt you should mine. The right column.
You will end up with an easy-to-climb dirt tower like this.
You can become the new mayor of Diggsburg if you find 10 Gold Keys and give them to Mayor Cole. Nine of them are in a fixed location inside the mine, while the tenth is found at Admiral Pulsar, 207 meters in the sky near the top of the map on the right side who is looking at a telescope.
The other 9 Gold Keys are found at these locations: