How to play
Each circle is an island, and its number says how many bridges end there.
Bridges run in a straight line, horizontally or vertically, between two islands. A pair of islands can be joined by one or two bridges, never more.
Bridges may not cross each other or pass over an island.
When the puzzle is solved, every island can be reached from every other island across the bridges.
Drag from one island to a neighbour, tap two islands one after the other, or tap the water between them; each tap cycles 0 → 1 → 2 → 0 bridges. On a keyboard, arrows move between islands and Shift plus an arrow builds a bridge. The puzzle is also widely known as Hashi.
Strategy and tips
- Count the neighbours. An island that can see n neighbours takes at most 2n bridges. If its number equals 2n — a 4 with two neighbours, a 6 with three, an 8 with four — every one of its connections is a double bridge.
- One below the maximum still helps. A 3 with two neighbours, a 5 with three or a 7 with four must have at least one bridge to each neighbour.
- Never cut off a group. Two 1s can’t be joined to each other, and two 2s can’t be joined by a double bridge, while other islands still wait — that pair would be sealed off from the rest. Medium sheets need this idea at least once.
- Watch for blocked paths. Every finished bridge rules out the connections that would cross it, which often leaves an island with only one direction to go.
- On hard and expert sheets you sometimes have to place a bridge in your head and see that it leads straight to a contradiction. The counting guide shows how that works.
Questions
- What do the levels change?
- The grid grows from 7×7 to 9×9, 11×11 and 13×13, with more islands each time. Easy sheets need only island arithmetic. Medium sheets need the rule against isolated groups. Hard and expert sheets need a one-step lookahead.
- Can bridges go diagonally?
- No — only horizontally or vertically, in a straight line between two islands with nothing in between.
- Why won’t a bridge appear?
- Either it would cross an existing bridge, or the two islands aren’t in a straight, unobstructed line. Crossings are refused automatically.
- How do I remove a bridge?
- Tap the bridge or the water between the two islands until it cycles back to zero, or use Undo.
- Is my progress saved?
- Yes. Every bridge you build is saved in this browser, along with the timer and the undo history, and the puzzle reopens where you left it.