Design Rationale of Level 9 Difficulty X

Author: maltz
Current Version: V2 Beta (June 9, 2011)

1. Enhance AI's technology to 200% of the rate of human players'. This enables the AI to pace with the ever-prospering human player and provide adequate challenge throughout the game.
2. Enhance AI's building construction and unit production to 300% of human players'. Such bonuses in Deity are at 200%. This also gives AI faster development and compensates for their humanized population (see below).
3. Enhance AI's world wonder construction rate to 150% of human players'. On Deity there is no such bonus.
4. Increase AI's start-up Settler combos to 3 . Each Settler comes with a Warrior escort and a Worker. On Deity, the AI starts with 2 Settler Combos. But the AI has no free Scout on Level 9.
5. Remove most of Deity AI's notorious "cheats": population growth (60% required food on Deity), unhappiness discount (60% unhappiness on Deity), and barbarian fighting bonus (60% on Deity). Testing reveals that the AI thrives well without these widely complained cheats.
6. Significantly reduce AI's gold by removing AI's discount on unit maintenance and building upkeep as well as the removal of bonus on population growth. Experiences revealed that Civ 5 AI's ever-growing gold reserve directly contributes to human's explosive growth, from both post-war unequal treaty and sinister or fortuitous pre-war resource and gold-per-turn deals.
7. Linearly scale up, from Immortal and Deity difficulty, (a) the range of land (now 9) and sea (now 22) of Barbarians (b) the efficiency of AI workers (now 225%), and (c) the AI's number of units supported by population (now 60% extra).