X-COM agents can be controlled somewhat automatically in their actions and reactions to hostiles depending on the settings you choose. To see what each button does, please consult your manual.
Safe Mode = Blue
The agent will seek cover first (even so far as to break line of sight with the foe) then engage in combat sporadically. This is a very similar attitude when panicking. Avoidance is paramount. This mode can sometimes be unhelpful because they will ignore your movement commands.
This mode is primarily used if you want the unit to avoid combat. This mode may not be used often with agents, and is quite redundant even with non-combat units under your control.
Cautious Mode = Green
The agent will position themselves behind an object, if one is available, and start firing if allowed to do so. They will sometimes run from an explosive (which is VERY BAD if a Boomeroid is close by). Your agents are aware of enemy positions as they shuffle for a position to fire, but they won't try to break line of sight. The best aspect of using this mode is that its an equal balance of avoidance and offence.
In real-time combat, if the agent is next to a corner and is under fire from an enemy, the agent will perform an automatic strafing manoeuvre. The agent will sidestep behind the wall for cover, and then sidestep out again every so often and return fire. This is extremely useful in places like wide doorways or when you are near any pillars.
This mode is a good all-rounder that is probably used mainly for its real-time combat sidestepping feature near corners.
Aggressive Mode = Red
Your agents will not seek cover or from grenades, your agents will fire towards hostiles even though there might be neutral security forces in the vicinity, your agents will happily run through a swarm of gunfire. In short, they obey your every command.
This is most common option which is used when fighting against enemy forces. You do not want your soldiers to stop firing when stationary. Offence is the best defence. If you have a defensive line outside the Alien craft on either side of the door, the last thing you want is for your Agents to get up and shuffle around for a position as the aliens bear down on them. This delay will get them killed. DON'T do the blue chicken dance.
The only time your agents will move of their own will is to escape fire or stun gas, but will shortly return to their original positions as soon as the gas or fire has cleared. It may help to move your troops to defensive positions manually instead of relying on the computer to do it for you.
This mode is best used when you want full control over the units you're currently controlling. It is by far the most popular and most players select it automatically and do not change it for the rest of the battle.
Note: If set to walk or crawl, an agent that has no weapons will run if they see an enemy, but resume walking/crawling once any visual contact is lost.
The agent will drop to the ground and will start to crawl. You need at least 2 free tiles in order to crawl. If in a confined situation, the soldier will stand instead.
Going prone reduces your size as a target and improves your weapon accuracy considerably. However you will move very slowly, and you will not be able to look over small obstacles like low walls. Brainsuckers cannot attach themselves when an agent is prone. They may jump nearby but land stunned.
In Turn based, TU movement consumption will be at its highest.
The agent will walk to your way point, or walk (usually, but will run sometimes) to a position when seeking cover. An agent is able to fire a weapon when walking but at reduced accuracy. Stamina drain and recovery is equal, so stamina is not consumed nor recovered while walking.
The only two reasons to walk is to fire on the move and to conserve stamina.
Your walking speed will vary depending on your speed and encumbrance levels. Single file formation and some disposition settings will override the walk and make the agent sprint in short bursts.
In Turn based, TU consumption and Stamina are consumed at the normal rate.
The agent will run until tired. Your soldier cannot fire their weapons when moving. Running is very dependent on Stamina. The more your Agent has, the longer they can run. Once they run out of stamina, they will default to walking until they regain some stamina.
In Turn Based, the TU consumption is reduced, while Stamina consumption is increased.
When ordered to kneel, agents will drop to a kneeling position as soon as they have no movement orders. Kneeling makes an agent a smaller target like crawling, but not as much and agents can peek over low objects with minimal exposure. Kneeling also makes aiming more steady so that agents get an accuracy bonus when kneeling, but again, not as much as when crawling.
Agents cannot move when kneeling and any movement orders will make them stand up and kneel again when the orders have been finished or cleared. Turning is still allowed. Agents will keep kneeling ( and standing up when moving ) for as long as the kneeling button is active.
In Turn Based, TU's are consumed whenever an agent has to stand up and kneel back down, so careless use can waste a lot of TU's as the agent kneels up and down between movement orders.
The formations control how groups of agents move in the battlescape. There are only two modes, formation and single file.
The selected agents will move to the next waypoint and stop in a chequered formation. They will attempt to move at their best possible speed depending on how tired they are and what movement modes have been set. This can cause faster soldiers to outdistance slower soldiers.
This is the default setting and most players never switch away from this mode.
Single File is a very interesting formation mode that is rarely used by most players due to a small loss in control that it has over the squad.
It causes a team of agents to dynamically coordinate amongst themselves, no matter how disarrayed they may seem, to fluidly form a single file formation, with the leader or point man always being the agent nearest the way point you specify. This restructuring of the single file chain always happens when you move the team as a group.
Once a single file chain is set up, each agent will have a buddy that they'll always follow. If you were to deselect the team and select the current leader, all of the other agents will automatically wander after the leader. If you were to break the chain and pick an agent in the middle, that agent becomes the leader of his or her own smaller single file chain. All of the chained agents will keep following their lead unit until they are issued a move order.
This chaining can be used on soldiers in other teams. With clever use of chaining small single-file formations of agents from others squads together, you could move two squads about the field by only controlling one squad in formation, with each agent in a secondary squad attached to an agent in the first squad.
Chains of agents have an irregular movement pattern. See the next section for details. This irregularity affects any agent that is part of a chain. Even if the lead unit is walking in Formation mode, this movement irregularity continues to hold true until the agent is removed from a Single File chain.
While a very clever walking mode, this movement irregularity causes a small loss in control, thus making it less generally desirable to use.
This mode fails because of the awkward movement, but is a great way of micromanaging small groups. You can use it to make an agent from a different squad follow a member from another squad automatically. By walking and using aggressive, these units can walk around and automatically use reaction fire on any enemies attacking the leading unit.
Walking and running in Single File
When walking in the single file mode, the agents may, for reasons unknown, vary their movement from a sluggish walk that is slower than the normal walk or may even sprint towards the nearest agent or (for the leading agent) way point in varying bursts. This is frustrating, therefore you cannot rely on them to walk or run normally when in single file.
If you must rush everyone to a particular location in a hurry, break out of single file and go to formation, and either move in formation or manually order your troops one at a time.
Combining Single File and Formation Mode
By using single file mode, you can link agents from any group with agents with another. For example, you can get six agents from another squad individually attach themselves to members of the main squad of six agents by making the agents in the first squad the lead unit in mini single-file formations.
Once the units are attached, you can select your main squad and then go back to formation mode. Your main squad will now be able to move about in formation, and the soldiers in the other squad will automatically follow the main squad and basically hover around the primary squad. Note however that because the soldiers are made up of mini single-file formations, your leading units may have their speed affected as if they were in single file.
You can also make longer mini-chains, however this can lead to a big mess agents getting in each others' way.
There are four different shot types that affect the fire rate and accuracy of weapons.
Prevents the agent from firing the weapon. It should be used if you want to capture a Alien and don't want it injured.
The slowest and most accurate of the Shot Types. When using this Shot Type units will aim at the selected target. Aimed Shots will caused the least damage to buildings, and it is best used when you want to minimize damage to the surrounding area.
The default Shot Type. It is faster then the Aimed Shot, but it is less accurate. When this Shot Type is selected units will fire a unaimed shot in the targets general direction. This shot is best used when the unit is close to the target.
The fastest and least accurate of the Shot Types. When this Shot Type is selected, the unit will fire short bursts at the target. It is best utilized at short ranges. If used indiscriminately, this Shot Type can cause unintended damage to the surrounding area.