The behavior of units in combat is governed by decision trees. With A Better ADVENT, almost all enemies get new AI trees, including the vanilla units. This has implications for the movement profiles the unit uses, which actions it considers doing and in which priority. The new AI trees are less open ended than the vanilla ones, giving every unit a clear role in combat. This is especially true for the enemy variants introduced by ABA.
Improvements to ability use
In the unmodded game, enemies use their abilities on cooldown whenever they can. Their decision tree sets up a very binary list of priorities and the first thing that can be used will be. A Better ADVENT links some abilities to other triggers, modifying these priorities if certain conditions are met. So instead of wasting a potentially good ability when better options may be available, it would only use that ability if it meets some extra criteria. These changes aren’t global, they are customized per unit. When an alien has only bad shots available, it might consider other options more strongly than it would otherwise.
Some examples for specific changes:
- Sectoids that have only bad shots available will go for Mindspin, hoping to panic someone out of their full cover into a more vulnerable spot.
- Demolitionist Troopers and Mutons use their grenades more aggressively than other units. If they don’t have a good shot on anyone, they will use their grenade on single targets as well, hoping to destroy their cover.
- Mutons may also use Suppress in that situation instead.
- Reduced priority for Mark Target on the second action of Captains leads to fewer “move, then mark” turns.
Examples for unit-specific AI changes
All the trees have been rebuilt from the ground, the amount of changes to the behavior resulting from that are way too numerous to fully list here. Here are some examples just to give an idea of what kind of changes this brings:
- Stunlancers are no longer pure melee units. They will use their guns to take any opportunity shots they come across. They will also sometimes randomly decide to use their gun instead of the stun baton.
- Turrets will no longer waste their second action. Most often, they will choose Overwatch if they don’t find a particularly good shot to take.
- Codices are more defensive, they will use their Teleport to keep distance and stay in cover, taking shots from there.
- Sectoids have a lesser probability to use Psi Reanimation and won’t use it at all if they have someone flanked.
- Shieldbearers no longer use their shield when they are already shielded due to another Shieldbearer on the field. They are also less likely to use the shield if they can only affect one or two units with it.