Civilization

What it is. A turn-based 4X (eXplore, eXpand, eXploit, eXterminate) where you grow a civilisation across millennia. No single system is deep per turn; the depth is layering — economy, tech, culture, diplomacy, military all tick together, and each turn’s small choices compound. Multiple victory paths (conquest, science, culture…) mean many strategies win. The famous symptom is “one more turn”: the next decision always dangles.

Player fantasy. Author of history. You steer a people from a single settler to a space-faring empire, and every era you unlock a new layer of play. The pull is the compounding — a good decision twenty turns ago is still paying off — and the horizon always holding one more reachable milestone.

Design DNA

The engine is layered compounding on a turn clock. Each system is simple in isolation; interacting, they generate deep decisions and long-horizon plans. A turn’s reward is always incremental and always sets up the next — the “one-more-turn” hook is a deliberate pattern-pacing-and-tension design: never end a turn without dangling an imminent payoff. The central risk is the snowball: 4X economies runaway (pattern-feedback-loops), so a leader accelerates away and the game dies at turn 100 of 300. Civ’s answer is comeback/catch-up brakes — tech diffusion, war weariness, per-city upkeep — so a lead is real but not sealed.

Load-bearing structures

Structure	Why it works
Layered systems	Economy/tech/culture/military each shallow per turn; interacting, they yield deep plans. Depth from breadth, not one hard system. → `pattern-emergence`.
Multiple victory paths	Science/culture/domination each win; players pick a lane, and the AI must contest all of them. → `system-build-diversity`.
Tech tree across eras	Research gates whole new layers of play; each era is a legible power/options spike. → `system-tech-tree`.
”One more turn” hook	Every turn ends with an imminent payoff dangling — a growth finishing next turn, a wonder two off. → `pattern-pacing-and-tension`.
Snowball with brakes	Runaway economy (positive loop) is deliberately countered (diffusion, upkeep, war weariness) to keep games contestable. → `pattern-feedback-loops`.
Perfect-information turns	Turn-based and pure-state; the whole game replays deterministically and clones for AI scoring. (FUN.md law 7).

What to steal

Layering over depth: many simple interacting systems out-produce one complex system for emergent decisions — and each is separately verifiable.
The “one more turn” pacing rule: never let a turn end without an imminent, visible payoff. This is the retention engine. → pattern-pacing-and-tension.
Multiple win paths as replayability and as a balance test: the AI must contest each lane, so no single strategy dominates. → system-build-diversity.
Snowball brakes: pair every runaway positive loop with an explicit catch-up mechanic, or the game decides itself early. → pattern-feedback-loops.

What’s just theme (drop it)

The real-world history — leaders, wonders, and civs are flavour on a layered-4X spine; a fantasy, sci-fi, or abstract skin plays identically.
The exact five victory types — the principle is “≥2 viable lanes,” not the specific set. → world-theme-vectors.
Hex map / literal units — one presentation of “regions you develop”; a node-graph or card layout carries the same layering.
Scale (millennia, huge maps) — the loop works at any scale; a single-session micro-4X keeps the DNA. → system-session-structure.

Composes into

genre-rts — the turn-based strategy neighbour (shared macro/economy DNA; Civ trades real-time mass for layered turns).
system-tech-tree — era research as the layer-unlock spine.
system-economy — the compounding faucets/sinks that fund every lane.
pattern-feedback-loops — the snowball and its required comeback brakes.
pattern-pacing-and-tension — “one more turn” as an explicit pacing design.

Twist seams

Civ but one session, one sitting (structure / constraint) — a micro-4X that resolves in 30 minutes; layering without the epic length. Pairs with system-session-structure.
Civ but you’re one citizen (perspective) — history from the ground: the empire is the environment, you a person living through its eras. Pairs with anchor-stardew-valley.
Civ but the map is a deck (mechanic-swap) — replace the hex world with a drafted card layout of provinces; layering survives the medium swap. Pairs with genre-deckbuilder.
Civ but comeback-only (constraint) — always play the underdog; the twist is a snowball you fight against, inverting the fantasy. Pairs with pattern-feedback-loops.