Each round shows two neighbouring countries merged into one blank shape. Everything else on the map is left out.

Click and drag to draw the border between them in one stroke. Drawing again replaces your line. When you're happy, press Submit.

The real border then appears over your line. You score up to 100 points. Every point along your line is scored on its own for how close it is to the real border, and your accuracy is the average of those scores. Being close in one place can't make up for being far off in another. That is then multiplied by how much of the border your line covers, so leaving part of it out costs you too, and by how close your line's length is to the real border's, so a line that scribbles back and forth, or cuts a winding border short, loses points. There are 10 rounds.

Zoom with the scroll wheel, a pinch or the +/− buttons. Pan by right-dragging, holding Space while you drag, dragging with two fingers, or switching on the ✋ pan button. You can keep zooming and panning after you submit.

Some pairs share more than one stretch of border, like India and China on either side of Nepal. Each stretch is its own round: the others are shown as a dashed line, and you draw the one that isn't shown.

Difficulty combines how well known the two countries are with how hard their border is to draw: a straight desert line is easy, a long winding one is not.

The map uses a true scale in every direction, so the scale bar holds across the whole view.