Turn Order

A not-so-brief summary of how the turns proceed in the game, starting with the beginning of the mission. Any suggestions or corrections are appreciated. Events occur in the order listed, at least, to the best of my/our knowledge.

Before X-COM Turn Begins

• Smoke and fire spread, dissipate, and do damage.
• Fatal Wounds check. Any units with Fatal Wounds lose one health per Fatal Wound at this time.
• "Anyone alive?" check for both sides. If failed by aliens, mission ends in success; if failed by X-COM, mission ends in failure. If both sides pass, continue. Note that Aliens under X-COM mind control will still allow the Aliens to pass this check; however, if all X-COM soldiers are under Alien mind control, X-COM will fail this check.
• Doors that automatically close are closed, like UFO doors in UFO and the Triton's hatch in TFTD. Any auto-closing doors that were open during an earlier save may not close again if the game is reloaded.
• Aliens Mind-Controlled on the previous X-COM turn are returned to Alien control.
• Energy refreshed for all units.

Beginning of X-COM Turn

• Stun damage decremented for X-COM units.
• Time Units refreshed.
• Morale check for all X-COM controlled units; if below 50, unit has chance of panicking/going berserk.
  • If failed, unit gains 15 Morale.
  • If unit panics, it will run to the south and possibly drop items in its hands.
  • If unit goes berserk, TUs are set to 255 and the soldier will spend them all turning in place and randomly firing Snapshots from their weapon.
• Player takes turn.

After X-COM turn ends

• X-COM grenades on the ground with the appropriate fuse setting detonate. Only grenades primed with an even starting number can detonate at this point, as well as any grenade whose timer expired while in a unit inventory which is now on the ground.

Before Alien Turn Begins

• "Anyone alive?" check for both sides. If failed by aliens, mission ends in success; if failed by X-COM, mission ends in failure. If both sides pass, continue. Note that Aliens under X-COM mind control will still allow the Aliens to pass this check; however, if all X-COM soldiers are under Alien mind control, X-COM will fail this check.

Beginning of Alien Turn

• Soldiers Mind Controlled during the previous Alien turn returned to X-COM control.
• Stun damage decremented for Alien units.
• Time Units refreshed.
• Morale check for all Alien controlled units; if below 50, unit has chance of panicking/going berserk.
  • If failed, unit gains 15 Morale.
  • If unit panics, it will run to the south and possibly drop items in its hands.
  • If unit goes berserk, TUs are set to 255 and the soldier will spend them all turning in place and randomly firing Snapshots from their weapon.
• AI takes turn.

Before Alien Turn ends

• AI takes Civilian turn (Terror Missions only).

End of Alien Turn

• X-COM grenades on the ground with the appropriate fuse setting detonate. Only grenades primed with an odd starting number can detonate at this point, as well as any grenade whose timer expired while in a unit inventory which is now on the ground.
• All Alien-thrown grenades detonate. (I've never seen the AI use a fuse setting other than 0)

Order of specific battlefield events

In progress; placeholder notes include reaction, mutual surprise rule, movement event checks.

Unit shot

• Base Damage calculated. 0-200% of damage rating for projectiles, 50-150% of damage rating for explosives.
• Resistances applied as multiplier.
• Armor value for affected plate subtracted from damage.
• Remaining damage value subtracted from unit's health. Sometimes, stun damage will also be added.

Unit takes damage from gunfire

• Armor plate that was hit is weakened based on health lost.
• "Still alive?" check; if health is 0 or below, unit fails and is killed. If passed, proceed.
• "Fatally wounded?" check; 0-3 fatal wounds will be applied to the area of the unit hit(if hit on the right side, fatal wounds will be on the right limbs, torso, or head; vice versa for the left side.) Aliens skip this check unless under X-COM mind control.
• If Fatal Wound is on a leg, multiply energy by (100%-(10% * number of fatal wounds))
• Recalculate stats based on new health percentage.
• Damaged unit loses Morale based on damage taken.
• "Still conscious?" check; if Stun damage exceeds health, unit falls unconscious. If passed, proceed with turn.

Unit killed

• "Mind controlled" check. If unit was mind controlled, unit is returned to standard ownership.
• Unit replaced by body type object dependent on armor type, named "Corpse".
• Death scream played.
• All items dropped.
• If flying, all items fall to ground.
• Morale for unit's owning side decremented.

Unit falls unconscious

• Unit replaced by body type object dependent on armor type, named with the unit's name(X-COM) or race and rank(Alien).
• All items dropped.
• If flying, all items fall to ground.

Unit healed with Heal command from Medi-kit

• 10 TUs subtracted from medic.
• 1 Heal charge subtracted from Medi-Kit
• "Wounded" check. If unit has Fatal Wounds on the targeted body part, test is passed, continue. If unit has no Fatal Wounds on targeted body part, test is failed, nothing happens.
• Unit regains 3 Hit Points and loses 1 Fatal Wound from targeted body part.

Unit healed with Stimulant command from Medi-kit

• 10 TUs subtracted from medic.
• 1 Stimulant charge subtracted from Medi-Kit
• "Tired" check. If unit has missing energy or Stun damage, test is passed, continue. If unit has full energy and no stun damage, test is failed, nothing happens.
• Unit regains 10 Energy recovers 4 Stun damage.

Unit recovers from stun naturally

• Unit stands up from ground in square, carrying no equipment.
• If square is occupied, unit wakes up one space to the north. If that square is occupied, continue clockwise until open square is found.

Unit revived with Stimulants

• Unit stands up from ground in square one space to the north. If that square is occupied, continue clockwise until open square is found.

Unit fires a weapon

• Time Units subtracted.
• Accuracy calculated.
• "Weapon loaded?" check. If ammo remains, continue. If not, end.
• Ammunition decremented.
• Projectile fired. If hit, Firing Accuracy experience counter is incremented.
• If firing an Auto shot, check ammo; if ammo remains, fire projectile again. If no ammo, end.
• Repeat above step once.
• Calculate damage.

Unit gets reaction fire opportunity

• Check initiative. If unit has higher initiative than enemy, proceed.
• Check TUs; if sufficient to fire the weapon, continue.
• Reaction experience counter incremented.
• Time Units subtracted.
• Accuracy calculated.
• Ammunition decremented.
• Projectile fired. If hit, Firing Accuracy experience counter is incremented.
• Calculate damage.
• Recalculate initiative.

Item thrown

• Assign ownership of item to thrower.

Explosive detonates(except proximity grenade)

• Increment Firing Accuracy experience once for each enemy caught in blast. If explosive was a grenade, experience is assigned to the last person the throw the grenade; if never thrown, experience is assigned to first soldier on transport, or first HWP if you have any.

Proximity Grenade detonation sequence

• "Mine" check. Has any unit moved into a space adjacent to the proximity grenade on the same elevation as said grenade? If passed, proceed. If failed, end. Checked after every square moved.
• Mine detonates.
• Increment Firing Accuracy experience once for each enemy caught in blast. Experience is assigned to the unit that detonated the proximity grenade.