Gameplay rules that are commonly used to add a tactical dimension to combat-oriented video and tabletop games—from Turn-Based Tactics, through Western RPG, to Tactical Shooters. At the most basic level, these rules revolve around positioning multiple player-controlled combatants in such a way that allows them to deal damage to enemy combatants, while avoiding being damaged or killed in turn.
- Equality Before the Rules. Both the players and their AI opponents play by the same rules (i.e. My Rules Are Not Your Rules and The Computer Is a Cheating Bastard are not in effect).
- Competing Objectives. Good tactical games give players additional mission-specific objectives or sidequests that run contrary to the main goal (defeating all enemies), such as taking captives, avoiding collateral damage, snatching up volatile resources, maintaining long-term morale, etc.
- Fog of War. Terrain features are revealed to the player only after they come into an allied combatant's viewing range. Dynamic parts of the level, such as enemies and moving/destructible objects, are not displayed (or not animated) unless they are currently within the viewing range of an allied combatant. Some games allow you to shroud units under a fog-generating unit or structure.
- Movement Modifiers. The movement speed of a combatant depends on the terrain he moves across, e.g. going down a slope is faster than climbing it, flatland is always easier to travel than hills, etc. Different units have different modifiers: cavalry or wheeled vehicles are slowed more than infantry in forests for example, and airborne troops can move over terrain that is impassible to ground troops.
- High Ground. If a combatant is positioned above his target, the accuracy, range, and damage of his attacks increase. By the same logic, a physically larger or mounted attacker may also have an advantage over a smaller target in melee.
- Destructible Environment. Many parts of the level, such as doors, walls, trees, bridges, etc., can be destroyed by applying explosives, excessive physical force or sufficient firepower to create shortcuts or to deny the enemy passage/cover. Some combatants may have abilities to repair them.
General combatant rules:
- Viewing Range. Different combatants dispel the Fog of War at different distances, e.g. recon units seeing much further than heavy-duty ranged units. Additionally, a combatant's line of sight is limited by terrain features and mobile objects. Viewing range can be extended artificially with special abilities/devices.
- Movement Speed. Different combatants can traverse different distances within the same time span on the same terrain, e.g. cavalry moving much faster than footmen. Movement speed and general maneuverability can be increased with special items or abilities.
- Sprint. A combatant can move faster than normal for a short time but cannot attack during (and possibly right after) the sprint. His maximum movement speed may be temporarily reduced afterwards, too. Certain abilities can increase the sprint speed or duration, up to unlimited sprint.
- Unit Specialization. Combatants with different training shine in some situations but are at a severe disadvantage in others, enforcing close cooperation within the team, e.g. a sharpshooter and a frontline fighter having vastly different ranges of engagement. Specialized combatants may have access to unique special moves.
- Leader Unit. A combatant specializing in frontline command boosts the efficiency and morale of all friendly combatants within limited range. His death, however, can have dire consequences, up to and including instant mission failure.
- Panic. When faced by overwhelming odds (e.g. a large number of allies dying or being pinned by heavy fire), a combatant can panic and start acting erratically instead of following the player's orders.
General combat rules:
- Attack Range. Different weapons have different minimum, maximum, and effective attack ranges. This concerns both ranged weapons (e.g. pistols vs. sniper rifles) and melee (e.g. daggers vs. polearms).
- Flanking. By attacking an enemy from his side or even from the back, a combatant can ignore his cover and generally has better chances of dealing damage. Alternatively, a unit's armor may be concentrated on one side, so it's much easier to pierce it from the other.
- Splash Damage. Some attacks, particularly involving Stuff Blowing Up, deal damage not just to the targeted combatant but to everyone/everything within a certain distance of the impact. Artillery shots, for example, can slightly damage any units next to its intended target. Can lead to Splash Damage Abuse, where the player causes Splash Damage to a target that isn't targetable directly.
- Friendly Fire. Friendly combatants are just as vulnerable to Splash Damage and attacks by panicking teammates as the enemy. Attacking and missing an enemy risks wounding a friendly combatant standing near him.
Ranged combat rules:
- Taking Cover. A combatant positions a solid object between himself and ranged attackers to minimize damage taken. Said cover can range from large pieces of the environment (hills, walls, crates, etc.), through mobile shields (e.g. ballistic riot shields), to Human Shields. The quality of cover often determines the amount of protection it provides.
- Covering/Suppressing Fire. A ranged combatant aids his ally's advancement either by taking a free reaction shot at any enemy who tries to hinder it, or by preemptively firing at the known enemy position to pin them down.
- Aimed Attack a.k.a. Called Shot. Instead of dealing normal damage, a combatant can attempt to disarm an enemy, hit his vital areas (such as his head) for massive damage, etc. at the cost of a lower success chance or a longer aiming time.
- Indirect Fire. A combatant uses gravity to fire projectiles at an enemy without establishing a direct line of fire, usually from behind cover. Firing can be blind or assisted by a forward observer.
- Blind Firing. The ranged combatant can bombard an area outside of his effective aiming range (or covered by smoke or the Fog of War) but within his firing range, giving him a (small) chance to hit an enemy in that area.
- Target Spotting. A ranged combatant has a much longer firing range than his viewing range and can attack enemies currently seen by his allies ("spotters") even when he cannot see them himself.
Melee combat rules:
- Charge. A combatant charges towards the target before striking it in melee, dealing additional damage proportional to the momentum gained. Especially relevant in Mounted Combat.
- Knockdown/Knock Back. A combatant knocks an enemy onto the ground, rendering them helpless for some time. Alternatively, the enemy is pushed away, either to dislodge them from cover, to shove them off an edge, to stagger them, or simply to put some distance between them and the attacker.
- Pincer Attack. An extension of the Flanking rule, melee combatants have much better chances of damaging an enemy when attacking him simultaneously from opposite sides.
- Crowd Control. A melee combatant has means of preventing enemies from moving past him or out of his melee range, such as a free attack against any enemy attempting it, a sweeping attack that pushes back anyone in range, or just cooking them with fire/microwaves/phlebotinum/whatever.
- Defensive Stance. A combatant sacrifices some of his offense to temporarily boost his defensive stats (especially against ranged attacks).
- Guard. Similar to Defensive Stance, but the combatant instead defends an adjacent ally (who may be incapacitated, busy, or otherwise unable to defend himself), potentially even Taking the Bullet for him.
Special ability rules:
- Concealment. Similar to Taking Cover rules, Concealment allows a combatant to get close to an enemy without alerting him to his presence, allowing for an easier takedown or targeting. Usually requires exploiting the terrain or a special ability, but can be countered by special detector abilities or items.
- Smoke Screen. A combatant deploys a smoke screen over a small area around himself or his allies to make them temporarily harder to hit or even to prevent the enemy from targeting them altogether (unless countered by thermal vision or equivalent). Combatants covered by smoke can usually aim at the enemies outside of it without penalty.
- Grappling Hook, Jet Pack, etc. Any ability or tool that allows a combatant to move vertically, giving him access to elevated positions that might not have been reachable otherwise.
- Context Action. At predetermined points, a combatant can perform a context-sensitive action (heal an ally, resupply ammo, pick a lock, disarm a bomb, hack a computer, etc.), leaving himself exposed to enemy fire.
- Rule Breaker. A combatant can break or ignore one of the basic rules above, usually balanced by some kind of trade-off.