All gold-producing buildings in your mine can be upgraded to maximize your profits. While you cannot merge buildings as you do with goblins, you can invest gold to increase their levels directly.
How to Level Up
To upgrade a building, tap the green button with the + sign.
Levels for Upgrade: The number on the button shows exactly how many levels you can buy right now with your current gold supply.
Upgrading Cost: The exact gold price for those levels is displayed at the bottom of the button.
Progress Bar: Located right above the button, this helps you track how close the building is to its next major income multiplier. The yellow part shows your current progress, while the lighter part previews where the bar will land after the upgrade.
💡 Milestone Rewards: Plan your gold budget carefully! Simply upgrading a building by a few levels provides a small boost. The massive income spikes happen when you completely fill the bar and hit a milestone. Plus, reaching a multiplier milestone rewards you with bonus Elixir!
Permanent Boosts and Automation
Aside from gold upgrades, you can permanently increase a building's baseline profit by using Cards to research advanced technologies in your collection.
"I spent Elixir, but the Mineshaft isn't automated!"
If you used your elixir to upgrade a building's card but the cart didn't start moving on its own, don't worry—your resources were not lost!
This simply means your building's card level was successfully increased, but it hasn't yet reached the specific level threshold required for full automation.
Check the card's details in your collection to see exactly what level is required to unlock automatic production. You may need to upgrade the card a few more times to activate it.
🔗 For a complete visual breakdown of the upgrade button, see our guide: Understanding the Upgrade Button Indicators.