A commission from the Board of Charts

Saltcartographer

The chain will not hold still. Every leg you sail, the whole archipelago turns about the Anchor Stone and stands somewhere new. You have a boat, a finite tank, and a blank sheet of paper.

1. Commit. Set a heading and a distance. The chain turns only once you have sailed, so you never steer into a position you have seen.
2. Look. Whatever breaks the water inside your sight circle is inked onto the chart exactly where you found it.
3. Read the chain. Sight the same island twice and the turn becomes a measurement. With the pencil layer on, extrapolate where the rest of the chain has swung to.
4. Mind the water. Three marks are named in your commission. The chain hides them under high water. Chart all three before the tank runs dry.

Arrow keys or A and D turn the heading, W and S set the distance, Enter sails the leg, C or Tab opens the chart, P toggles the pencil. On a touchscreen, drag the dial and use the stepper.