When a new game is started, four difficulties can be chosen: Easy, Normal, Hard, and Impossible. Difficulty cannot be changed once the game has started.
In addition to affecting hard numbers such as damage rate or research speed, difficulty also affect diplomatic proposals. Easy difficulty will see more generous offers and gifts. In Hard and Impossible not only do the gifts disappears, you may actually be demanded to hand out territories.
Despite the name, with good tactic and strategy (and perhaps some help from this wiki), Impossible difficulty is not impossible to win for a veteran of the game.
Afterlight's Design Document (in Czech) may contains detailed difficulty formula.
|(ResearchTimeMod) Research speed multiplier.|
|(ManufacturingTimeMod) Production speed multiplier.|
|(TrainingSpeed) Training speed multiplier.|
|(TrainingDecay) Decay speed of partial Training.|
|Level Up Speed||1.4||1.0||0.85||0.75|
|(ExperienceMod) Experience multiplier. (Also apply to strategic)|
|(HealingNormal) Healing speed when not in ward or surgery.|
|(FactionSpreading) Speed of alien faction expansion.|
|(RaidDestroy) Chance that Rocket Base destroys intruders.|
|(HostilityBonus) Environment hostility level adjustment.|
|(AverageSquadsCount) Average number of enemy squad.|
|(EUdefaultLevelUpPoints) Enemy attribute budget baseline.|
|(HostilitySuitBase) Environment damage caused by suit breach.|
|(EnemySeeingMod) Enemy sensory range multiplier.|
|(EnemySeeingMod) Player character sensory range multiplier.|
|(DmgModFromEnemy) Enemy damage multiplier.|
|(DmgModToEnemy) Player character damage multiplier|
|(FriendlyFireWeight) Friendly fire weight adjustment.|