Each player in Xconq runs a side. The concept of a side is somewhat abstract in Xconq; units in a game belong to sides, but the sides themselves are not attached to any particular unit. Sides 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 the distinction between 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 a player, but in one game you may play the Canadian side, and in another the Klingon side. During a game, there will always be a side for each player, and vice versa. The distinction is most important during game setup and restart of saved games, since that is when 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 development and espionage.
There are several possible tech thresholds for each type of 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 a tech to own that you must have in order for a unit to be on your side and get the benefit of its eyes and so forth. After that there is a tech to use, which you must have in order to make the unit do any actions. In order to build a unit, you need to have achieved the tech to build.
Games may allow you to research advances using your side rather than units. For instance, Civ-type games work this way; your "wise men" work on an advance, without being associated with any specific city or other unit. If the game includes side research, the interface will ask you which of several possible advances you want the side to research. You can also ask not to research, perhaps if you want to conserve resources consumed by research. Once a topic is chosen, the research runs automatically until the advance is achieved, at which point Xconq announces the advance and asks you what you would like to pursue next.
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 sufficiently high tech level.)
A self-unit is a unit 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" 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. In any, the game will define which types may be self-units.