Port

The Port is a Building that spawns Trade Ships and allows you to build Warships.

Cost

Ports scale in price based on number of owned ports AND factories.

City cost
Port/factory number	Gold cost
1st	125,000
2nd	250,000
3rd	500,000
4th+	1,000,000

Mechanics

Warship spawning

Warships can only be bought if a player owns a port. The game will try to spawn the warship from the closest fort to where the warship is being deployed.

Trade Ship Spawning

Ports check every 10 ticks if they should spawn a Trade Ship. Ports higher than Level 1 "roll the dice" once for each level (the same as if they were separate entities).

Spawn chance is calculated based on number of owned ports, number of owned trade ships, and number of trade ships on the map.

$spawnChance = \frac{1}{⌊ \frac{25}{\sqrt{baseChance * portMultiplier}} ⌋}$

Where baseChance is equal to 1 when you own less than 3 trade ships (exclusive), otherwise it is:

$baseChance = 1 - \frac{1}{1 + e^{(- \frac{\ln (2)}{10} * (numOfShips - 55))}}$

In short, this means that the more ships there are on the map, the less likely more ships are to spawn, with a small number having only a very small effect. At 25 ships, the chance is 88%, at 55 it's 50%, at 100, it's just 4%.

$portMultiplier = \frac{1}{1 + \frac{portsOwned}{10}}$

More ports = lower spawn rate per port, but higher spawn rate overall.

There is no spawn cap.

Trade Route Selection

Ports will only trade with other players (not their own ports). Trade partners are prioritized in this order:

Closer ports get double chance of being selected (proximity bonus)
Allied ports get double chance of being selected
A port's level determines how many times it is added to the pool of destinations.

Trade ships are automatic, free to build, and don't count against unit limits.

Gold Generation

Gold earned is based on Manhattan distance (which means the sum of the absolute differences in x and y coordinates) between ports and the number of ports you own:

$tradeShipGold = ⌊ b a s e G o l d * b o n u s ⌋$

BaseGold scales with Manhattan distance. There is also a debuff for small distances, less than around 400 Tiles, this means that short trade routes are extremely unprofitable, and should be avoided. See the graph for details.

baseGold = \frac{100, 000}{1 + e^{- 0.03 * (distance - 300)}} + 100 * distance

Bonus is a value which is dependent on the number of ports you own. The more ports you own, the smaller the increase; the medium point is at 4 ports with a bonus of approx. 1.9. The bonus is an example of hyperbolic decay.

$bonus = 1 + 2 * \frac{portsOwned - 1}{portsOwned + 4}$

Both the source and destination port owners receive the full amount.

Longer trade routes are more profitable (linear scaling with distance).