Classification of Turn-Based CombatSome of the ways to classify turn-based combat are as follows:
When do you give commands?
- Start of the Turn. At the start of each turn, each player gives the orders to every unit under their command. These orders are then carried out either simultaneously (so-called "Simultaneous Turn Resolution") or in order of initiative (see below).
- Before the Unit Acts. The player gives orders to each unit individually and they are carried out immediately.
When is it a unit's turn to act?
- Initiative Queue: Each unit, regardless of allegiance, is assigned an initiative score (partly randomized, partly dependent on its stats) at the start of combat: the one with the highest initiative gets to act first (as long as it is not killed), then the second highest, and so on. After the lowest initiative has acted, the next turn begins. The highest initiative may act first again, or the initiative may be recalculated every turn. A Visual Initiative Queue may be displayed.
- One Side, One Turn: Each player (whether human or AI) gets to move each of their units individually in any order on their turn, while the enemies stand still. Afterwards, the other player gets to move all of their units in the same manner, and so on.
- One Side, One Move: Each player gets to move with a single unit on their turn, after which the other player moves one of theirs, and so on. Chess works this way.
See also Sliding Scale of Turn Realism.
What can you do on your turn?
- Action Types: On its turn, each unit can perform one action of a specific type, e.g. a "move action" and an "attack action", which allows it to move into position and attack the enemy, or attack and move away. Some action types can be traded for others (e.g. the attack for another move—but not vice versa), while some things don't require using up an action at all.
- Action Points: Each unit gets a pool of "action points" each turn, which represent its quickness. Taking an action consumes a varying number of points from this pool until it is empty and the unit can no longer act in this turn. Depending on implementation, ending the turn early either discards unspent action points or (partially) preserves them for the next one.
How far can you move on your turn?
- Field Grid: The battle area is overlaid with a grid of square- or hexagon-shaped fields, and a unit can move up to a certain number of fields on its turn. A single field may only be occupied either by an inanimate obstacle, or by a single living unit at one time (although allies may be able to pass through each other's fields).
- Continuous Terrain: There is no grid, and the unit can move to any point on the battlefield where the collision detection algorithm allows it to, with the cost of the move calculated by the appropriate pathfinding algorithm.
Can you act out of turn?
- Delayed Action. A unit can choose not to attack on its turn, but instead to delay the attack until the enemy does something specific (e.g. comes into shooting range), effectively getting to act on the enemy's turn.
- Attack of Opportunity. Under certain conditions, a unit can make a free attack out of turn, triggered by an enemy's action, such as firing a ranged weapon at close range, or attempting to disengage from melee.