Technology Trees

Research is how a country invests its scientific capacity. Every project is an optional capability, doctrine or institution: completing it grants a lasting bonus, a one-off effect, or access to something else in the game, such as a law, a National Focus, a weapon system or another project. Projects run in the slots provided by Research Centers, several at once.

The 1946 catalog holds about 195 projects, with historical dates from 1945 to the late 1990s.

Categories and trees

The research screen separates six categories into sixteen trees:

Each tree is drawn as a canvas of projects in rough historical order, with lines to the projects they lead to. Requirements from other trees are shown as links, and the detail pane for a project lists its requirements, its effects and everything it Enables.

Requirements

A project can require:

• Earlier research. All listed prerequisites must be complete. Some projects instead accept any one of a group: Fission Weapons needs the Atomic Theory Program and either Uranium Enrichment Centrifuges or Plutonium Production Reactors.
• A national focus, a policy or a date. Industrial Robotics, for example, cannot start before
• Access. A few projects belong to one country only, such as the United States' high-altitude reconnaissance and stealth aircraft programmes or the Soviet Union's ground-effect craft and titanium-hulled submarines.

Some projects are rival doctrines that exclude each other for good. A country chooses Deep Battle Doctrine or Active Defense Doctrine for its army, and Counterforce Targeting or Second Strike Capability for its nuclear forces; completing one closes the other.

A full research queue does not lock a project: technical eligibility and free slots are checked separately.

Cost and duration

The same project costs different countries different amounts, and the price changes over time. Each project has an authored cost and duration, measured against a reference economy of $50 billion. When a project is started:

1. Economy size. Cost is scaled by the square root of GDP relative to $50 billion, kept between 0.05 and 4 times. A country four times the reference size pays twice the authored cost; one a quarter the size pays half. The largest economies all pay the same, four-times ceiling.
2. Ahead of its time. Each project has a historical year. Starting it early multiplies both cost and duration by 1.25 for every year early, counted up to ten years. Once the year has passed, there is no penalty.
3. Research partners. A live research-sharing treaty partner (Technology Sharing, Joint Research Program or Scientific Cooperation) that has already completed the project cuts its cost and time by 24% per partner, to at most 40%. See Treaties.
4. Research speed. Duration is divided by the country's research speed (below).

There is no general diffusion: other countries having finished a project does not make it any cheaper for you unless they are your partners. The cost and duration are fixed when a project starts and paid in daily installments that add up to the quoted price; a research day that costs more than the day allows waits for a later one.

Research speed

Research speed starts at 1 and adds:

• Research Speed from laws, research and focuses;
• 10 times the country's research spending as a share of GDP, so spending 1% of GDP on research adds 0.10 (Research Spending);
• half the distance of the country's Education from 50%, so full education adds a quarter and none subtracts a quarter.

Speed never falls below 0.25.

Sharing classes

Each project carries a sharing class. Civilian projects can be shared through a Scientific Cooperation clause; restricted and strategic projects, which include most weapons work, cannot.

What finishing a project gives

• Lasting modifiers for as long as the country has the research, including projects granted at the start. Unit bonuses apply to existing forces at once; nothing needs rebuilding.
• One-off effects such as prestige: the first three countries in the world to complete a project earn tiered prestige, and the world's first is announced. Landmark projects such as Fission Weapons, Thermonuclear Weapons or Human Genome Mapping grant extra prestige.
• Capabilities. Many projects unlock a choice without making it. Universal Primary Education allows the Mass Education law but does not adopt it; Experimental Pile Reactors allow a civilian nuclear programme. The ongoing cost belongs to the adopted policy.

Food research shows how effects feed other systems. Precision Irrigation lowers Famine risk by 10%, and Cold Chain Distribution lowers famine losses by 20%. Medical and food projects raise Public Health.

The number of projects a country has completed is its unlocked technology count, which feeds the world research ranking and National Agendas.

Research and other systems

• National focuses gate some of the largest programmes, such as strategic weapons and space missions, and many focuses in turn need research. See National Focus.
• Nuclear weapons are a programme rather than a project: research gives the know-how, but the bomb also needs focuses, plants and a test. See Nuclear Program.
• Espionage can steal progress on a project from a country that has completed it, up to three quarters of the work. See Espionage.

Starting research

Each country opens the 1946 campaign with a list of technologies already completed, reflecting its industry and institutions. Industrial powers start well along several trees; developing countries must lay foundations such as electrification before attempting computing, modern agriculture or a modern grid.

How the AI researches

AI countries keep to their era and their means. They never start a project more than five years before its historical year, nor one costing more than half a percent of a year's GDP; under high Threat Levels, that limit doubles for military and strategic research. They favour military projects at war and economic ones at peace, weigh their famine and health risks, and value projects by the paths and capabilities they open. An AI researches the bomb itself only while its nuclear policy pursues weapons.