Minor issue: sometimes several "countries" (not actually countries, but dependent territories) have the same flag, but the game only accepts one answer as valid.

that's my favourite feature :)

Solver:

window.setInterval(() => { var g=currentFlag.commonName; checkGuess(g); document.getElementById('search-input').value = g;}, 600);

Nice, but I wrote one 10x as fast:

window.setInterval(() => { var g=currentFlag.commonName; checkGuess(g); document.getElementById('search-input').value = g;}, 60);

/s