Name any city in the region to begin. It drops a dot on the map and reveals an amount of new land proportional to its population — on open, unclaimed ground that is a circle around the city.

Only new land counts. Any part of that circle that is already yours, or sea, or outside the region is made up for by pushing the circle further out until the city has found its full share. So a town deep inside ground you already hold still moves your frontier outward, and a coastal city reaches across the water. There is no limit on how far a circle can grow — a city boxed in by your own land, or on a small island, jumps straight to the nearest unclaimed ground, however far away, and that ground becomes reachable.

From then on you may only name cities that fall inside a circle you already own. Each one adds its own circle, and the covered area spreads. Getting across a mountain range or a stretch of desert means knowing the little places along the way.

Stuck on the wrong side of an ocean? An airdrop places one city anywhere, no connection needed. You get a few at the start and earn another every 20 cities.

The bar tracks how much of the region’s land you have covered. The notch on it is the ceiling — the coverage you would reach if you named every single qualifying city. In a region with more people than land to share it sits at 100%; in a thinly settled one like Oceania the land outlasts the people.

A city means a settlement of 50,000 people or more. There are 11,540 of them on Earth.

Suggestions appear once you have typed four letters, and they never say which cities are in reach — they are there to settle spellings, not to hand you the answers. Type less than that and you need the full name. Accents and capitals don’t matter, common alternative names work (Munich, Cologne), and a country after a comma picks between namesakes: Springfield, US.

Switch the map to satellite to play on real imagery: everything starts grey and dim, and each circle you claim is revealed in full colour. The Sat/Map button on the map flips between the two mid-game.

Cities: GeoNames (CC BY 4.0). Coastlines and land area: Natural Earth. Satellite imagery: Esri, Maxar, Earthstar Geographics.