Combat

Current concept

The outcome of a combat is influenced by several factors:

• The attackers attack & defense value.
• The defenders defense & attack value.
• The units' health.
• The units' experience

The outcome of a battle is calculated in several rounds. In each round the attacker gets to hit the defender, while the defender hits back after that. In each round a damage value is assigned, which is subtracted from the other units health. If the health is reduced to 0 (or less), the unit dies.
In simple terms, the damage value could be expressed like that:
 
Damage = ( [ Attack_A * Health_A * Experience_A ] - [ Defense_D * Health_D * Experience_D ] ) * Random
 
I'll give you an example:
Let's say a 100% healthy chariot (A/D: 3/1) with a 20% experience bonus attacks a 80% healthy spearman (A/D: 1/2) with no experience bonus. In the first round the basic damage is
[ 3 * 100% * (1 + 20%) ] - [ 2 * 80% * (1 + 0%) ] = 3,6 - 1,6 = 2.

Do I really need to have both attack and defense values in this scenario? Yes, I believe it to be more realistic...

Visions

In the future, combat in Altera Terra will be a mixture of the slightly modified Civ concept as described above and the combat resolution of Battle Isle. This means, that surrounding units will influence the outcome of a battle. If there are additional units of the attacker present in the surrounding tiles, this will add to the strength of the attacker. Likewise will happen for other units of the defender. The strength of the influence depends on the position (in Battle Isle these used to be called "flanking" and "blocking"):
A flanking unit is a unit that holds a position on a tile that borders both the attacking and the defending unit.
A blocking unit is one whose tile only borders on one of the units.

If several units are within one tile, there are additional effects. The player decides, which unit will attack. On the defending tile, always the strongest unit (regarding defense value, health and experience) will be the chosen defender. However, the experience and health of other units present will modify these values.
On the defending tile, the experience will be the maximum of the chosen defender and the average of the defender and the unit with the highest experience. So let's say that there's a musketeer with 1* experience (+10%), but there is a worker with 4* experience (+60%), the musketeer will be treated as a musketeer with an experience bonus of +35%.
The health value for both attacker and defender will be calculated from all units present: health = max { health of unit; avg_health of all units on tile}