Research is the progression system that unlocks new buildings, new districts, and repeatable global bonuses. Research is performed globally for your kingdom and costs Science, so a completed research applies across all of your villages. Researches are organised into tiers (1 through 8), and almost every research has a prerequisite that must be completed first.
Tier: the research tier, from 1 to 8. Higher tiers cost more Science.
Requirement: the prerequisite research. A research becomes available only once its prerequisite has been completed.
Unlock: what completion grants. Tiers 1 to 7 unlock a specific building or a new district; tier 8 researches grant repeatable global bonuses instead.
The Science cost of a research is not fixed. It is computed dynamically from the research's tier, the player's level, and the server's elapsed time, so the cost a player sees in-game will differ from server to server and over the lifetime of a single server.
Pausing research
Ongoing research can be paused. The science progress for paused research is saved, but the cost isn't. If you obtain a higher tier, or the cost is reduced through server lifetime, the science required to complete a paused research will increase or decrease, depending on the effect. Saved progress isn't affected by tiering up.
Research tree
Research dependency tree across 8 tiers
The tree branches from two tier-1 entry points, Town Defenses (the military / defensive line) and Apprenticeship (the economic / labour line), and fans out from there. Tiers 1 through 7 unlock buildings (and, at tiers 3 and 4, the Industrial and Trade districts) that cannot be obtained by any other means. Tier 8 does not unlock buildings; it contains repeatable global projects intended for the late game.
Tier 8 researches do not unlock buildings. They grant global, repeatable bonuses, and each can be completed multiple times, with the cost scaling on subsequent completions.
