Each player in Xconq runs a side. The concept of "side" is somewhat abstract in Xconq; units in a game belong to sides, but the sides themselves are not attached to any particular unit. Side often represent countries, but not invariably; they may be factions, governorships, or alliances, or just a convenient division of the game's units.
It is important to be clear about sides and players. A side is a part of the simulated world, while a player is the actual real-world person or program that is playing the side. You yourself are always the player, but in one game you may play the German side, and in another the Klingon side. During a game, there will always be a player for each side, and vice versa. The distinction is most important during setup and restoration of saved games, since you can choose which players go with which sides.
Each side can have a name and associated parts of speech, such as a noun for individuals on the side and an adjective to describe anything belonging to the side. A side may also have an emblem and one or more colors for displays to use. Some game designs preset all this, while others let you personalize as desired.
In games with two players, your interaction is usually pretty simple, i.e. bash on each other. In games with many players, some human, some mechanical, it is possible to have a variety of relationships, ranging from complete trust to complete hostility.
A side can trust another side. This is like a close ally - you can enter each other's transports, you share view data, and so forth. Trust is a two-way relationship; both you and the other side each have to declare you want to trust the other. You can do this at any time. You can also, unilaterally, withdraw your trust in another side at any time. There are no preconditions or caveats for trust.
You can make your side be controlled by another side. This is basically a surrender that lets you stay in the game, because the controlling side can manipulate any of your units as if they were its own. The controlling side also has the option of allowing or forbidding you to move your own units. The relationship is strictly one-sided, and only the controlling side can release the controlled side. (Note that this is a way to have several people play on a side; have one player run the controlling side and be helped by several other players running controlled sides, usually with agreed-upon responsibilities.)
Diplomacy is to do and say // The nastiest thing in the nicest way. -- ISAAC GOLDBERG (1938)
If you don't want to declare a special relationship with another side, but still want to make some sort of adhoc arrangement, you can create an agreement. An agreement is a sort of generalized treaty; it consists of a number of terms agreed to by a number of signers, which are sides. Agreements may be public or secret, and you can declare them to be enforced by Xconq if the terms are in a form it understands. An agreement that just says "help each other out" cannot be evaluated by the computer!
[Agreements are not completely implemented.]
In some game designs, technology and research are important. These games give each side a set of tech levels (or just tech for short), one for each type of unit. The tech level represents the technological knowledge needed to see, operate and build a type of unit. Tech levels never decrease, at least in the Xconq universe, and they can be increased by research and espionage.
There are several tech thresholds for a unit. First there is
tech-to-see, below which you will not even be aware of the
existence of a unit (consider barbarians unable to see spy satellites
passing overhead). Then there is tech-to-use, which you must
have in order to make the unit do any actions. The
tech-to-understand and tech-on-acquisition are points at
which your side can increase its tech level just by owning a unit, and
finally the tech-to-build is what you must have to create new
units of the given type.
In some games, several sides may be very similar to each other, while being very different from other sides in the same game. For instance, the game might have several sides that are different tribes of barbarians, but they are more like each other than, say, Romans. These similar sides can be given the same side class. Units may then be restricted to be usable only by the sides in a particular class. (Note that this is different from tech level, which allows units to be used by any side that has managed to acquire a sufficient tech level.)
A self-unit is one that represents your whole side in some way. For instance, in a dungeon exploration game, your "side" might consist of an adventurer (you), your possessions, your followers, and perhaps more. In such a case, if the adventurer dies or is captured, then the game should be over, at least for you.
Usually the self-unit will be set up by the game design, and all you
have to do is to be aware that losing the self-unit permanently ends
your participation in the game. Some games might have "self-unit
resurrection" (self-resurrects) which just means that if another
type of unit is available when the current self-unit dies, then that
another unit becomes your new self-unit. For instance, admirals would
leave their sinking flagship and board another ship, thus "transferring
the flag". (Admirals presumably being more valuable than captains, who
are supposed go down with their ships!) Some games may also allow you
to change self-units manually (self-changeable). In any, the
game will define which types may be self-units (can-be-self).