Example Scenarios Comparing CA and Sequential TB Systems


Limiting Time Spent In Line Of Sight Of The Enemy



One group of units is about to assault a room in a bunker which is defended by an unknown quantity of defending units, which may or may not know about the imminent attack and which direction it will come from.  The room has multiple doors/windows which the defending units may be covering with their weapons.


The attacking unit is ordered to move past an open doorway to obtain a glimpse of the units defending a room.  The unit runs past the doorway so that the defending unit does not have enough time to fire an accurate shot, if he is able to fire at all before the running unit disappears from his view.


With Sequential TB

The running unit is only visible for a fraction of a second in game world terms, but if the defender interrupts he can use as many APs as he has available and perform as many actions as those APs allow.  This lowers the tactical depth of the game because the defender’s actions are not affected by the running unit’s tactic of only being visible for a short period of time.


In sequential TB it does not matter that the running unit is only going to be visible for a split second.  If the defender interrupts he can still use whatever actions he has enough APs to perform.  Even if moving units are harder to hit, the defending unit can use more APs for the shot.  The defending unit may have less APs to spend later in that turn, but this is a gameic rather than a tactic as it is caused by the turn system and not the game world.


Even if the APs available for the defender’s action were limited, the limit would have to be based on assumed actions of the running unit - i.e. how many APs it will spend while in the defender’s line of sight. Yet that only handles the case of a single unit running past a doorway or window.  If two units run past in a single turn, one next to the room wall and one slightly further away, did they run past with one some distance after the other or did they run past together side by side.  If they ran past at different times which one ran past first is important because the second one will be more likely to be shot at.  All these situations are handled implicitly in a multiple action game world but are either ignored in a sequential action game world or arbitrary assumptions used to decide upon an AP limit.


If the defender is not directly facing the doorway the chance of an interrupt may be lower, but if the defender gets focus he can use APs to turn with the only penalty being less APs to use for subsequent actions.  Again the tactics of the running unit has little influence on the situation compared to the AP stores of the units.


With Concurrent Action

In this game model, the defender only has the time the running unit is visible in which to take a shot.  The defender requires time to turn to face the door, raise his weapon, aim, fire or perform any other action.


If the unit is facing the doorway he may have enough time to raise and fire a poorly aimed shot at the running unit.  If the defender is not facing the doorway the running unit will have likely disappeared from sight by the time the defender has turned.  The game may allow units to cover an area with their weapon raised, and if the defender has been ordered to cover the particular doorway he may be able to fire an aimed shot.  Even if the unit is facing or covering the doorway he may have such poor reactions that he cannot fire in time or can only fire a poorly aimed shot.  There are far more possible outcomes than that provided by an interrupt system where it is ‘all or nothing’.


In the case of multiple running units running side by side the defender will have no extra time to shoot, if one is running past some distance after the other then the defender may have time to cover the doorway with his weapon before the second unit arrives.  This is all handled implicitly by the multiple action model of the game world, whereas with sequential models it is up to the game’s designers to try to regain the lost tactical depth by adding specialised non-game world systems.


The Concurrent Action model retains the tactical options lost by using a sequential model.  The actions the defending units can take against the visible attackers depend primarily on the actions of the attackers instead of how many APs the defenders have.




Dependency On Line Of Sight



A friendly unit ‘A’ is next to cover (crouched beside a large rock, wall or some equivalent cover large cover) in combat with enemy ‘B’.  Unit A needs to reload his weapon (a modern projectile weapon such as an SMG or assault rifle).  Unit A moves behind cover out of the line sight of enemy B and reloads his weapon.


With Sequential TB

In sequential TB reloading costs APs like most other actions.  If the unit reloading is visible to an enemy, that enemy may interrupt or get opportunity fire.  The represents the enemy attacking the unit as it reloads.  However in this example unit A is out of sight of the enemy when it performs the reload action, and the enemy cannot act because he cannot interrupt or get opportunity fire.


With Concurrent Action

In a Concurrent Action game world the enemy B is active while unit A is reloading.  Enemy B can use the time to move, throw a grenade, or otherwise alter the tactical balance in their favour.


A sequential action game world does not allow this and looses two features because of it.  Firstly the tactical options presented when the player determines that an enemy behind cover is reloading and the player taking advantage of that are not available.  Secondly the tension of reloading is lessened; in a multiple action game world the unit has little or no defence while reloading his weapon, this makes it a tense period until the unit is combat ready again.  Even then the enemy’s actions while the unit was reloading may have changed the combat situation in the enemy’s favour, creating a new and more desperate situation for the player.


In a sequential action game world this tense period of reloading is reduced to an action costing the unit 5 APs or similar, after which he can continue fighting the enemy without them having a chance to act.  If the unit reloads at the end of his turn then the enemy can act during their turn, but this is not due to the unit reloading.




Switching from RT to TB


In games where the game is RT until combat begins, the point at which the switch to TB is made greatly affects the combat situation.  For instance consider a situation where a melee character A is running toward enemy B to attack him.  If the player controlling A switches to TB then orders A to run, the run order will use up APs and A will only have enough for perhaps 1-2 attacks.  If A runs while in RT mode then the player switches to TB, A will have all his APs and can make more attacks, even though in the game world the two scenarios are the same.  In both cases the enemy may interrupt A while moving or attacking.


In games such as Silent Storm the player can enter TB mode manually and the game does not enter TB mode immediately when an enemy is sighted.  This leads to situations where the player tries to position his units without triggering the switch to TB mode if this will give him an advantage.  Controlling the switch from RT to TB is obviously a gameic and not a tactic.


The problem persists in games such as Jagged Alliance 2 which use "TB on sighting" (this is also an option in Silent Storm).  While it is sensible to try and avoid the enemy seeing your units, in these games the player can gain a tactical advantage by preventing his own units from sighting the enemy.  This is most apparent when moving multiple units into position, as this requires synchronising their movements in real time while trying to ensure that no unit sees an enemy.  Again the actions in the game world do not change, but because of the switch to TB a unit which moves into position in TB mode will have less APs than the same unit moving into position in RT mode.




Investing Time



Three friendly units A, B and C are about to attack two patrolling enemy units which are unaware of the units’ presence.  Unit A targets one enemy and B the other, and C needs to decide which target to pre-aim at or to aim for neither.  In the case where one target is killed by A or B but the other is not, C adds his firepower to the remaining target.


The dilemma is that the player may order C to pre-aim at one target or to only fire after A and B have performed their actions.  Pre-aiming while A and B are performing their actions will allow a better shot at the target but at the expense of taking more time to target the other enemy if the first one is killed by A or B.


With Sequential TB

Units A and B can perform their actions before unit C, so the player is never faced with the dilemma.  Unit C does not loose any APs while waiting for A and B to perform their actions.


With Concurrent Action

Unit C must either wait for units A and B to fire and then pick a target, or pre-aim at one enemy, which will decrease the time it takes to shoot at that enemy but increase the time to shoot at the other.




Item Running


A unit ‘H’ urgently requires medical aid but the nearest medical kit is held by unit ‘A’, who is so far away that it would require many turns of movement to reach unit H with the kit.  Unit A with the medical kit uses most of his APs to move towards unit H then uses the last of his APs to pass it to unit ‘B’ who still have APs remaining.  Unit B repeats this process, moving towards the next unit in the chain until a unit reaches H and provides medical help.


This may take multiple turns but it will be far fewer turns than if unit A himself had brought the kit, especially since units nearer unit H but not in position to help the chain can be moved to more appropriate positions before the medical kit arrives.


The medical kit effectively spends the entire turn with unit A, but then also spends the entire turn with unit B and whichever other units form the chain for that turn.  The sequential TB game world allows unit H to receive medical aid sooner than otherwise possible, lessening the requirement to issue medical kits to many units in case they are needed.