Where the facts come from

CO₂ emissions

“Rank these countries by CO₂ emissions in 2024” 150 cards · checked 2026-09-30

• Our World in Data: CO₂ and Greenhouse Gas Emissions CO₂ from fossil fuels and industry in 2024, from the Global Carbon Budget. Land-use change is not included.

Estimates differ between datasets, so countries in one puzzle are always at least 25% apart.

CO₂ per person

“Rank these countries by CO₂ emissions per person in 2024” 150 cards · checked 2026-09-30

• Our World in Data: CO₂ and Greenhouse Gas Emissions CO₂ from fossil fuels and industry in 2024, from the Global Carbon Budget. Land-use change is not included.

Estimates differ between datasets, so countries in one puzzle are always at least 25% apart.

Cities by latitude

“Rank these cities from north to south” 113 cards · checked 2026-09-30

• GeoNames: GeoNames geographical database City-centre coordinates in decimal degrees.

Cities by longitude

“Rank these cities from west to east” 113 cards · checked 2026-09-30

• GeoNames: GeoNames geographical database City-centre coordinates in decimal degrees.

Country population

“Rank these countries by population” 150 cards · checked 2026-09-30

• United Nations: World Population Prospects 2024 Mid-2024 total population, millions. Read from the Our World in Data copy of the dataset.

Country size

“Rank these countries by total area” 151 cards · checked 2026-09-30

• Wikipedia: List of countries and dependencies by area Total area (land plus water) in km², as given by the United Nations Statistics Division.

Energy use per person

“Rank these countries by energy use per person in 2024” 77 cards · checked 2026-09-30

• Our World in Data: Energy dataset Primary energy use per person in 2024, in kilowatt-hours, from the Energy Institute and the US EIA.

Estimates differ between datasets, so countries in one puzzle are always at least 25% apart.

Life expectancy

“Rank these countries by life expectancy at birth” 144 cards · checked 2026-09-30

• Wikipedia: List of countries by life expectancy Life expectancy at birth in 2023, both sexes, from the United Nations World Population Prospects table.

Countries in one puzzle are always at least 3 years apart, so small differences between sources never change the answer.

Median age

“Rank these countries by median age” 150 cards · checked 2026-09-30

• Wikipedia: List of countries by median age We use the CIA World Factbook 2024 column. The Factbook itself was discontinued in February 2026, so this table is where its figures are still published.

Items in one puzzle are always at least 3 years apart, so small differences between sources never change the answer.

Mountains

“Rank these mountains by elevation” 56 cards · checked 2026-09-30

• Wikipedia: Wikipedia articles for each item Each item is checked on its own Wikipedia article.

Renewable power

“Rank these countries by the share of their electricity from renewables in 2024” 149 cards · checked 2026-09-30

• Our World in Data: Energy dataset Share of electricity from renewables in 2024, from Ember and the Energy Institute.

Hydro, wind, solar, bioenergy and other renewables. Countries in one puzzle are always at least 10 points apart.

Rivers

“Rank these rivers by length” 42 cards · checked 2026-09-30

• Wikipedia: List of river systems by length Length of the whole river system, measured from its farthest source. Lengths vary between sources.
• Wikipedia: Wikipedia articles for each item Each item is checked on its own Wikipedia article.

River lengths vary between sources, so rivers in one puzzle are always at least 10% apart.

Atomic number

“Rank these elements by atomic number” 60 cards · checked 2026-09-30

• IUPAC: IUPAC Periodic Table of the Elements

Boiling point

“Rank these elements by boiling point” 49 cards · checked 2026-09-30

• Wikipedia: Boiling points of the elements (data page) The recommended value at standard pressure.

Very high boiling points are hard to measure, so elements in one puzzle are always at least 50 °C apart.

Element density

“Rank these elements by density” 46 cards · checked 2026-09-30

• Wikipedia: Densities of the elements (data page) Density near room temperature in g/cm³, the value recommended for use on Wikipedia.

Element discovery

“Rank these elements from first to last discovered” 22 cards · checked 2026-09-30

• Wikipedia: Discovery of chemical elements Year of first discovery or isolation, as given in the table.

Some discoveries are credited to different years, so elements in one puzzle are always at least 5 years apart.

Melting point

“Rank these substances by melting point” 55 cards · checked 2026-09-30

• Wikipedia: Melting points of the elements (data page) Values from the CRC Handbook of Chemistry and Physics, at standard pressure.
• Wikipedia: Wikipedia articles for each item Each item is checked on its own Wikipedia article.

Planets & moons

“Rank these worlds by diameter” 31 cards · checked 2026-09-30

• NASA: Planetary Fact Sheet Diameter in km, as given in the table.
• NASA JPL: Planetary Satellite Physical Parameters Mean radius; diameter is twice the radius.
• NASA Science: Ceres Mean diameter from the Dawn mission.

Space milestones

“Rank these space milestones from earliest to latest” 31 cards · checked 2026-09-30

• Wikipedia: Timeline of space exploration Events not on the timeline are checked on their own Wikipedia article.
• Wikipedia: Wikipedia articles for each item Each item is checked on its own Wikipedia article.

Star distance

“Rank these stars from nearest to farthest” 32 cards · checked 2026-09-30

• Wikipedia: List of brightest stars Distance from Earth in light-years, as given in the table.

Distances to faraway stars are uncertain, so stars in one puzzle are always at least 30% apart.

Animal speed

“Rank these animals by top speed” 14 cards · checked 2026-09-30

• Wikipedia: Fastest animals Top recorded speeds, which vary by study.
• Wikipedia: Wikipedia articles for each item Each item is checked on its own Wikipedia article.

Approximate; animals in one puzzle are always at least 30% apart.

Animal weight

“Rank these animals by typical adult weight” 16 cards · checked 2026-09-30

• Wikipedia: Wikipedia articles for each item Each item is checked on its own Wikipedia article.

Approximate, using adult males where the sexes differ; animals in one puzzle are always at least 50% apart.

Food calories

“Rank these foods by calories per 100 g” 19 cards

• USDA: FoodData Central (SR Legacy) Energy in kcal per 100 g.

Longest lives

“Rank these animals by the longest recorded lifespan” 42 cards · checked 2026-09-30

• Human Ageing Genomic Resources: AnAge: The Animal Ageing and Longevity Database Each animal is checked on its own AnAge entry.

Oldest individual on record, in the wild or in captivity.

Pregnancy length

“Rank these animals by how long a pregnancy lasts” 32 cards · checked 2026-09-30

• Human Ageing Genomic Resources: AnAge: The Animal Ageing and Longevity Database Each animal is checked on its own AnAge entry.

Typical gestation; animals in one puzzle are always at least 20% apart.

Historic events

“Rank these events from earliest to latest” 42 cards · checked 2026-09-30

• Wikipedia: Wikipedia articles for each item Each item is checked on its own Wikipedia article.

Inventions

“Rank these inventions from oldest to newest” 33 cards · checked 2026-09-30

• Wikipedia: Wikipedia articles for each item Each item is checked on its own Wikipedia article.

Landmarks

“Rank these landmarks by height” 34 cards · checked 2026-09-30

• Council on Tall Buildings and Urban Habitat: The Skyscraper Center Architectural height, or tip height for towers.
• Wikipedia: Wikipedia articles for each item Each item is checked on its own Wikipedia article.

Best Picture winners

“Rank these Best Picture winners from oldest to newest” 91 cards · checked 2026-09-30

• Wikipedia: Academy Award for Best Picture Year the film was released, as listed in the table (the ceremony is held the following year).

Films are dated by release year. Films in one puzzle are always at least 3 years apart.

Hit songs

“Rank these songs from oldest to newest” 41 cards · checked 2026-09-30

• Wikipedia: Wikipedia articles for each item Each item is checked on its own Wikipedia article.

Movie runtime

“Rank these movies by runtime” 28 cards

• IMDb: IMDb title pages Theatrical cut runtime in minutes.

Video games

“Rank these games by release year” 39 cards · checked 2026-09-30

• Wikipedia: Wikipedia articles for each item Each item is checked on its own Wikipedia article.

Olympic golds

“Rank these countries by all-time Summer Olympic gold medals” 31 cards · checked 2026-09-30

• Wikipedia: All-time Olympic Games medal table Summer Games gold medals up to and including Paris 2024.

Race distances

“Rank these races by distance” 19 cards · checked 2026-09-30

• World Athletics: Competition and Technical Rules
• IRONMAN: IRONMAN race distances 3.86 km swim, 180.25 km bike, 42.2 km run.
• World Triathlon: Competition Rules Standard (Olympic) distance: 1.5 km swim, 40 km bike, 10 km run.

Sporting firsts

“Rank these sporting firsts from earliest to latest” 29 cards · checked 2026-09-30

• Wikipedia: Wikipedia articles for each item Each item is checked on its own Wikipedia article.

Stadium size

“Rank these stadiums by capacity” 37 cards · checked 2026-09-30

• Wikipedia: List of stadiums by capacity Capacity as given in the table. Capacities change with renovations.

Capacities change with renovations, so stadiums in one puzzle are always at least 10% apart.

Summer Olympics

“Rank these Summer Olympics from earliest to latest” 20 cards · checked 2026-09-30

• International Olympic Committee: Olympic Games

Team size

“Rank these sports by players per side on the field” 30 cards · checked 2026-09-30

• Wikipedia: Wikipedia articles for each item Each item is checked on its own Wikipedia article.

Company founding

“Rank these companies by year founded” 41 cards · checked 2026-09-30

• Wikipedia: Wikipedia articles for each item Each item is checked on its own Wikipedia article.

Gadget launches

“Rank these gadgets by launch year” 28 cards · checked 2026-09-30

• Wikipedia: Wikipedia articles for each item Each item is checked on its own Wikipedia article.