Sources and checks

Every answer in Size Duel and Older Than was checked against two independent sources. The first 120 sizes and 150 dates were read from Wikidata (structured data under CC0) with the statement, rank and unit recorded, and compared with an independent source: a national encyclopedia (Store norske leksikon, Lex/Den Store Danske, Treccani, Hrvatska enciklopedija, Sapere.it, the Great Russian Encyclopedia), the Animal Diversity Web, NASA fact sheets, the US National Park Service, sports rule books or another official page. Where Wikidata had no matching value, two other sources were used. The source pages were downloaded on 2026-10-19 by a server job and compared automatically (the quote must appear in the page).

The second batch (149 sizes, 200 dates, added in October 2026) was researched by a separate research agent (Codex), which read at least two independent publishers for every fact and recorded a short verbatim quote from each: agencies, museums, rule books, national encyclopedias and university references; Wikipedia never counts as a source. A server job then fetched every cited page again and looked for each quote; for 38 facts a page could not be read by the server (blocked or a PDF), and the research agent’s own check of that quote is used. Measurements keep their exact scope (head and body without the tail, main span between towers, launch mass with fuel), and dates keep their exact milestone (patent granted, first published, first performed, opened). All game text was written for Size Duel by Claude, the AI build agent that made these releases; no human editorial review has been recorded yet. Values that sources disagree on are shown as ranges and only duel things outside that range; items whose “first” date is disputed were left out.

Population Duel uses the World Bank’s World Development Indicators: total population (SP.POP.TOTL) for 2025, the latest year, for every country that has it (Vatican City has no World Bank value and is not in the deck), and land area (AG.LND.TOTL.K2) for the density shown on the reveal. Population and area: The World Bank, World Development Indicators (CC BY 4.0). The countries list (193 UN members and two observer states), regions (UN M49) and the cross-checks are documented with the dataset.

Further North? uses 382 well-known cities and capitals. Each city’s latitude is Wikidata’s coordinate for the city centre (CC0), cross-checked against Natural Earth’s populated places (public domain). 18 cities were left out: 11 because the two sources disagree by more than 10 km, 5 because only one source gives coordinates, and 2 because the sources disagree on which country they belong to or their status is disputed. Country silhouettes on both decks are drawn from Natural Earth (public domain) and are not to scale.

Measures and units

Values are stored in metres and kilograms and shown in metric, with imperial units as a setting. Animals use typical adult values with a range taken from the sources; planets and moons use their diameter; mountains use the height of the summit above sea level. Dates are years in the Gregorian calendar (before 1582 the year shown is the year the sources give; no day-level conversion is needed at year precision). Populations are mid-year estimates; latitudes are in degrees north or south of the equator.

Every value

Every date

Countries and cities

Every country has a page with its population, land area and a link to its World Bank data (Population Duel deck); every city has a page with its coordinates and Wikidata item (Further North? deck).

Drawings, text and font

All 255 silhouettes, 157 symbols, the group symbols and the brand mark are original SVG drawn in code for Idistic, with no tracing of photographs and no third-party artwork; each has a provenance record with its hash. Country silhouettes come from Natural Earth (public domain). Notes and explanations are written for Size Duel; no encyclopedia text is reused beyond the short quotations. Brand and product names (for example Airbus A380) are used only to name the thing measured. Font: Bricolage Grotesque, © The Bricolage Grotesque Project Authors, SIL Open Font License 1.1, served from this site.

Corrections are welcome at support@twindle.nl; a changed item gets a new revision, and published daily rounds keep their duels.