Test Freshwater Sea/Lake Requirements

[QuintillusCFC]

Related to #355 ; see WildWeazel's comment:

This will be referenced for a few things: "coastal" production options, "fresh water" proximity, and the food yield (is that a hard coded +1 for freshwater coast?). I think any sea or ocean tiles automatically mean it's considered open sea.

We need to test:

• What exactly is the maximum size of a freshwater sea? I think it's about 20 tiles but is it 19? 20? 21?
• Does it count for fresh water proximity (e.g. being able to build nuclear power plants)?
• How does the food bonus work, relative to saltwater coasts/seas? What about commerce?
• Do sea and ocean disqualify a body of water from being a freshwater sea?
• Confirm that boats cannot be built on freshwater seas

Don't forget to disable the Despotism penalty when testing for food/commerce bonus.

Please document your findings, either via sourced material (e.g. CFC threads) or with your own testing as the source.

We will likely make aspects of this configurable, but want to have a legacy-compatible rule set as well.

[WildWeazel]

On Discord, Lumadous reports that 20 tiles or less is considered fresh water on all map sizes, and that fresh water tiles do not confer any "coastal" effects nor receive any water bonuses. The game will never generate sea or ocean tiles in freshwater bodies, but placing them makes no difference.

To answer your questions directly:

• 20 inclusive
• yes
• No change with harbor, etc. I forgot to ask about freshwater sea and ocean yield but coast always gets +1 food.
• No, but only occur on custom maps
• Correct

Given that, I'm thinking we should have a salt/fresh flag on each water tile for the rules to check, and automatically apply it when importing maps. That way each rule is free to determine how to treat each, and custom maps are free to assign them arbitrarily.

[pcen]

#430 will implement this without the ability for custom rules (though, we don't really have any configurable rules at the moment)