OPERATION MANUAL // CITY//TRACE
HOW THE GAME WORKS
Every UTC day, one city is selected server-side for every player on Earth. The scan starts as a flat, fully encrypted 3D surface. Five data channels decrypt in a fixed sequence — TERRAIN//RELIEF, then ROAD//NETWORK, RIVER//SYSTEM, POP//DENSITY and finally DEMO//LANGUAGE — each unlocking only after the previous one. Each reveal permanently spends points and adds an animated layer to the same persistent model. You have three attempts to name the city. No distance hints, no direction hints — only the city's own geographic fingerprint.
SCORING
Every trace starts at 10,000 points. Deductions: ROAD//NETWORK −1,500 · RIVER//SYSTEM −1,100 · POP//DENSITY −1,800 · TERRAIN//RELIEF −1,600 · DEMO//LANGUAGE −1,300 · each incorrect guess −700 · time decay up to −1,500 (reached at 180 seconds). A failed trace scores zero ranked points but still records your statistics. All scoring is computed on the server — the browser only ever shows a projection.
ANTI-CHEAT COORDINATES
Active puzzles never contain real-world coordinates. During preprocessing, each city is projected into an artificial local coordinate system: geometry is centered on a protected point, normalized, quantized and stripped of every label, name and identifying property, then stored under an opaque asset id. The browser receives coordinates like [−0.032, 0.015] — never longitude and latitude. Layer data is only delivered after a reveal is recorded, one channel at a time.
GEOGRAPHIC DATA SOURCES
City layers are built from real geographic data at build time: road and waterway geometry from OpenStreetMap (© OpenStreetMap contributors, ODbL), population from the European Commission JRC's GHSL GHS-POP 2025 grid (CC BY 4.0), and elevation from the AWS Terrain Tiles dataset (Mapzen terrarium composite of SRTM, GMTED, NED and ETOPO1, including offshore bathymetry). Geometry is simplified, quantized and stripped of all names during preprocessing — no live map APIs are called during gameplay. See DATA_SOURCES.md in the repository for exact provenance.
PRIVACY
A guest session is created automatically so you can play instantly; it stores only a random identifier. Linking Google attaches your display name and avatar to leaderboard entries. We never display email addresses, and leaderboard documents contain only leaderboard-safe fields: display name, score, time, clue count, guess count and success state.
ATTRIBUTION
ROAD AND WATER DATA © OPENSTREETMAP CONTRIBUTORS (ODbL)
POPULATION DATA: GHSL GHS-POP E2025 R2023A, EUROPEAN COMMISSION JRC (CC BY 4.0)
ELEVATION DATA: AWS TERRAIN TILES / MAPZEN TERRARIUM (SRTM, GMTED2010, NED, ETOPO1 AND OTHERS)