That's still a lot of stuff, but I hope it's understandable.General principle: Leave as much functionality of the game mechanics to the rule text
of the cards themselves. Special abilities like "flying" are not explained in
this general ruleset. The rules below are truly general and define a working
game. But any card may also change these rules.
Zones that every player has:
deck stack: Face down stack of cards
city stack: Face up stack of cards of type "city"
grave stack: Face up stack of cards that are dead
hand: A set of cards that is hidden from enemy players
battlefield: An area of cards of type "unit" and "promotion"
Every card has a name, a type and a ruletext. The types are "city", "unit" and
"promotion". Every card starts in the deck, and is moved to the hand. Cards can
be placed on the city stack or into the battlefield at no cost.
unit: In addition to the general elements, a unit has a subtype that describes
its role in the world of Wesnoth. Furthermore a unit has a base attack and base
defense value. Whenever the damage that a unit receives in a turn is greater or
equal to its defense value, the unit is put on the grave stack. Units can also have
levels. Every unit starts at level 0 and can rise in levels by attaching
"promotion" cards to it. The level of a unit is equal to the number of promotion
cards of a specific faction. Depending on the level, different abilities may
be available for that card.
promotion: A promotion card can be attached to a unit and thereby rise its
level. Promotion cards usually come with additional bonuses.
city: A city is placed on the top of a player's city stack. Every game starts
with each player searching their libries for a city card and placing it on the
city stack. The deck is shuffled afterwards. Whenever a player has no more cards
on the city stack he/she loses the game. Even though a player can have several
city cards on the city stack, only the topmost city card is active. Every city
card has an attack and defense value. Whenever a city receives damage greater or
equal to its defense value in a turn, the city is removed from the top of the
city stack and placed at the bottom of the city stack of the player who dealt
the last damage to it (This simulates the conquest of cities).
During each player's turn that player draws a card from his/her deck. If that is
not possible, that player loses the game. The active player can attack other
players. Whenever a player attacks, the defending player may choose units for
defense. The defenders deal damage to the attackers and receive damage from the
attacking units. Any damage that is not being covered by the defending units is
dealt to the city card on top of the city stack of the defending player. The top
city card can also deal damage to attacking units if it has an attack value
greater than zero.
During a player's turn he/she may place cards from his/her hand into other zones
controlled by him/herself. Unit cards can be placed into the battlefield,
promotion cards can be attached to unit cards and city cards can be placed on
top of the city stack.
When there are no more enemy players, the game is won.
Let me give you an example for levels of units: Say we have a gaian archer with the following ruletext:
We can symbolize these level requirements similar to MTG mana costs. There can be faction-specific level requirements and faction-unspecific level requirements.ranged 2 (This unit does not receive damage from other units in combat with a lower ranged value)
level GG: ranged +3
level GG1: ranged +2
level GR: Add 1 damage to every attack.
Here we have three levels. Two of them require only gaian promotions and one of them requires one gaian and one red banner promotion to be activated.
Once this unit reaches the gaia level 2, its ranged ability is increased by 3 (so that it is at 5). Once it has another promotion card attached to it (faction does not matter), the range ability increases by another 2 (and thus becomes 7).
Once it has one gaian and one red banner promotion, it deals 1 additional attack damage.
And thanks to ngoeminne for suggesting the name "cities".