Tap an island, then another it can see, to lay a bridge. Do it again to make it a double bridge — two side by side, counting as two for both islands — and a third time to take it away. Dragging from one island toward the other is surer on a touch screen. With a keyboard, Tab to an island and press an arrow toward its neighbour.
Join every island to the others with bridges. The number on an island is how many bridges end there. Bridges run straight across or down, never cross one another. Two islands can be joined by one bridge or by a double bridge — two side by side — and a double counts as two on the number of each island it joins. When every number is met and you can walk from any island to any other, the board is solved.
Tap an island and then another it can see to lay a bridge between them, or drag from one toward the other — on a phone, dragging is surer. Do it again to make it a double bridge, and a third time to take it away; tapping a bridge does the same. A bridge that would cross another is refused. With a keyboard, Tab to an island and press an arrow key toward the neighbour you mean.
Four boards. The first can be done by counting alone, the second needs you to keep the network in one piece, and the last two are larger ones where at some point you will have to try a bridge and see whether it leads anywhere — once on the third, three times or more on the last.
Start with the islands that have no choice: a 4 in a corner, a 6 at an edge, an 8 anywhere. Two 1s can never be joined to each other, nor two 2s by a double, or they would be cut off from the rest. The day prints well if you prefer to work it out in pencil.
A new day starts at midnight UTC. Your progress is kept in this browser, so you can leave a day half done and come back to it, and every day already published stays playable from the archive.