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Pick a continent. You meet a few countries at a time, by region, then the game asks where each one is, its flag and its capital.
Get one right and it waits longer before asking again. Miss it and it comes back in a few questions. You're asked about a country just before you'd forget it.
Countries fill in on the map as you learn them: striped while you're learning, pale once you know them, full colour when you still know them a day later. The colours themselves only tell neighbours apart.
There's also a daily challenge, the same ten questions for everyone, and duels you can send to a friend as a link.
Practice as often as you like: pick from four, type the answer, or name every country you can against the clock.