Castle, buildings, construction queues and speed-ups

Short answer: the Castle is the heart of your Turf. Its level caps every other building, and you can run one construction at a time unless you unlock Construction Queue 2. When an upgrade has 3 minutes or less left, you can finish it for free.

What the Castle does

Your Castle level caps your other buildings. From level 3 on, a building can only be upgraded to a level that is no higher than your Castle level. If it is higher, the Upgrade window lists the Castle as a requirement and shows Not Met.
Raising the Castle unlocks new buildings and features. Two you can check: the Embassy and the Battle Hall need Castle level 10, and so does the Soul Sanctum. A locked building tells you “Requires Castle level N.”
The Castle screen shows your Max Army Size, Max Deployable Heroes in Army, Max Help, Wall HP, resources and heroes in one place. Castle upgrades also unlock more Station slots for heroes that defend your castle.
The Wall is your first line of defense. If it is damaged it defends poorly, so repair it after attacks. Wall HP also repairs by itself while it is below max.

Build a new building

Tap an empty plot in your city and pick a building under Choose building.
Check the cost and the requirements, then Confirm Build.
The building starts in a construction queue and finishes when the timer ends.

You can only build as many of one type as the game allows (“Limit reached! No more buildings of this type allowed.”). If Cannot build! appears, tap it for the reason. Some buildings cannot be built by hand at all.

Upgrade a building

Tap the building and open its Upgrade window.
Read the Requirements. Each row shows a building and Reach Level N. A row that says Not Met means you must upgrade that building first. The message “You need to upgrade these buildings first” lists them.
If you are short on resources, turn on Use Bag resources automatically. The game then uses only the suggested amount of your Bag resource items. It never buys anything for you.
Tap Upgrade. The building shows “Upgrading…” until the timer ends, then “Upgrade Success!”.

If the price changed while the window was open, you see “Upgrade cost changed. Please review it and try again.” Open the window again and check the new cost.

Production buildings (Farm, Stone Mine, Lumber Mill, Ore Mine) fill up to a storage cap and then stop producing, so collect from them regularly. Each level raises production per hour and storage. Upgrades and training use all four resources, so keep food, stone, wood and ore balanced.

Construction queues

You start with one construction queue: Construction Queue 1. While it is busy you see “Another building is under construction. Please wait.” You cannot start a second construction until the first finishes, is cancelled, or is sped up.

Construction Queue 2 lets you run two constructions at once. Open the queue 2 slot (shown as “Construction Queue 2 not unlocked”) and choose Unlock Construction Queue 2:

Option	What you get	Price (GEM)
Rent 3 days	Queue 2 for 72 hours. The slot shows “Rent expires in …”.	200
Permanent	Queue 2 for good.	499

You pay with GEM. Your balance shows as “Your GEM”, and you see “Not enough GEM” if you are short. AURO payments have ended, so AURO cannot be used.
You cannot rent while a rental is active (“Your Construction Queue 2 rental is still active.”). You cannot buy while you already own it permanently (“You already own Construction Queue 2 permanently.”).
With both queues in use you see “All construction queues are busy. Please wait for one to finish.”
If you tap an option and it says “Still processing. Tap the same option again to retry. You won’t be charged twice.”, tap the same option once more. The payment is only taken once, and the retry finishes unlocking the queue.

Speed up a construction

There are three ways to shorten a timer.

Free Speed Up. When an upgrade has 3 minutes or less left, the Speed Up window shows “Free Speed Up is ready” and a Free button. Tap it to finish at once. Earlier than that, the game says “Too much time left to speed up for free. Please wait”. This applies to building upgrades.
Speed Up items from your Bag. Open Speed Up, choose Auto use (“Automatically uses Speed Up items”) or pick the items yourself, then Confirm Speed Up.
Some upgrade windows can also finish the upgrade instantly for GEM. The price is shown before you confirm.

Read the item name before you use it

The time is in the item name, and the items are used up when you confirm. Take care with the two names that look alike:

Speed up (30 minutes) takes 30 minutes off.
Speed up (30 days) takes 30 days off. Do not use it by mistake.

Items come in 1, 5, 10, 15, 30 and 60 minutes, then 3, 8 and 15 hours, then 24 hours, 3, 7 and 30 days. Which items work on a building upgrade:

Item type	Works on building upgrades?
Speed up (…) (plain)	Yes. It also works on research, training and healing.
Constructing speed up (…)	Yes, buildings only.
Research speed up (…)	No. Research only.
Training speed up (…)	No. Training only.

If you pick an item that is much longer than the time left, the game warns you (“…which is somewhat wasteful as your waiting time is much shorter. Are you sure you want to proceed?”). If you go ahead, the building finishes and the whole item is used.

Cancel an upgrade

Open the building and choose Cancel, then Confirm. The window warns: “You’ll only recover 50% of the resources spent on this. Cancel anyway?” The building goes back to its previous level. You cannot cancel once the timer has ended (“the building upgrade … has already been completed”).

Demolish a building

Choose Demolish on the building and confirm. Demolishing is not instant:

It takes half of the build time of the building’s current level.
Speed-ups can only bring the timer down to 5 minutes. Below that, speed-ups stop working (“Speed-ups stop working once 5 minutes or less remain.”).
The Instant Demolish item finishes a demolition outright. You use one at a time. It shows how many you own, and you can Buy & use one for 50 GEM.
Some buildings cannot be demolished: Workshop, Embassy, Battle Hall, Trading Post and Garrison Tent (“This building cannot be demolished.”).
An Infirmary cannot be demolished if its wounded troops would no longer fit (“The infirmary is full, unable to demolish the structure.”).

If something goes wrong

What you see	What to try
Timer ended but the building still says Upgrading, or “This building is already upgrading.” / “Another building is under construction.” with a free queue	The screen can lag behind the server by a moment. Wait a minute, then close and reopen the game.
“Requirements not met. Upgrade the required buildings first.”	Open the Upgrade window and upgrade the buildings marked Not Met. Remember the Castle cap.
Not enough resources	Use Use Bag resources automatically, or collect from your production buildings.
“Building is unavailable right now. Please try again later.”	Try again in a few minutes.
Queue 2 unlock stuck on “Still processing”	Tap the same option again. You are not charged twice.
Used the wrong speed-up item	Items are used up when you confirm. Open a ticket with the time and the item name; support will look at your account.

If an upgrade is still stuck after you reopen the game, open a ticket from Setting → More → Support (see Contact support). Include the building name, its level, the message you saw, and when it happened.

Related: Research and the Academy.