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D.8 How huts upgrade
Huts have three levels - level 1, 2 and 3.
When you first build a hut, it will always be a level 1 building, also known as small hut.
After some time, it will upgrade to level 2, also known as medium hut.
After another minutes, it might upgrade to level 3, also known as large hut.
The huts always have two bars - a green one, indicating when a new born is going to be born, and a red one, called the upgrade bar. When this red bar reaches the top, the hut will upgrade to the next level. Obviously there will be no upgrade bar in a large hut, because there is no upgrade to the level 3 large hut.
To build a hut, you need 3 wood piles. When the hut wants to upgrade to level 2 medium hut, you will need 2 more wood piles. When the hut wants to upgrade the the final level (level 3 large hut), you need another 2 wood piles. The upgrade bar moves faster depending on how many braves are inside of that hut - as well as the green bar. Green bars move faster the higher level the hut is.
Only huts can upgrade - not training huts or vehicle ones.
Blue's large hut.
Blue's medium hut.
Blue's small hut.
As you can see, a large hut can have 5 units inside and has a green bar, but not a red (upgrade)bar.
Blue's small hut. You can see the red (upgrade) bar is on top, this means the hut is really close to get upgraded to level 2 (medium hut).