This section describes random things.
Technology, or tech for short, is useful when technological development is important to a game. There are several ways to use it.
One use of tech is to track the results of research.
You do this by setting the initial tech of a side to (say) 0,
then requiring a certain tech (say 60) in order to build a desired type.
If a research action adds 1 to a side's tech, then it will
take 60 research actions to gain the necessary level.
The number of turns, of course, depending on how many actions
the researcher can do each turn, and how many researchers
are available. So for instance, 10 researching units results
in the work being done in 6 turns instead. You can limit this
schedule acceleration by setting tech-per-turn-max.
Another use of tech is to differentiate sides.
Suppose you want to do a game involving earthlings and space aliens.
The aliens can have satellites overhead that earthlings don't even
know are there, they have equipment earthlings couldn't use even if
they were able to capture it. However, earth scientists might learn
something from it. To do all this, use tech-to-see and friends.
Tech is fundamentally tied to unit types. However, many games have
a number of unit types that share technology. For instance, advances
in bomber technology usually lead to advances in fighter and surveillance
aircraft. The tech-crossover table is available for this purpose.
Normally a player runs the side as a whole, and all the units on that side are disposable and interchangeable. However, you require one unit to represent the player personally among the units of the player's side; this unit is the self-unit. What this means is that if that unit is captured or dies, the player loses the game instantly. All the other units on the side will behave normally as for losing, either going over to the side that captured the player, becoming independent, or disbanding.
The idea is to increase the player's motivation for self-preservation. This is useful to introduce a risk of capture, assassination, and so forth. It also prevents bizarre and unrealistic strategies in some games.
For instance, it sometimes happens in empire-building games that players end up switching countries, because each captured another's country and neglected to defend their own. If each player got one capital city, and that city were to be a self-unit, then the owner would have to defend it at all costs!
To make this happen, you could do something like this:
(set self-unit-required true) (add capital-city can-be-self true) (add capital-city start-with 1)