Rules
- Bridges run horizontally or vertically between two islands, in a straight line over open water.
- Two islands can share one bridge or two, never more.
- Bridges cannot cross each other or pass over another island.
- The number on an island is how many bridges end there.
- When you finish, every island must be reachable from every other one.
Drag from one island towards a neighbour, tap two islands in turn, or tap the water between them to cycle through no bridge, one bridge and two. Undo and redo go back as far as you like, and the hint shows the next bridge that can be proven from what is on the board.
Where to start
Count the neighbours an island can see. An 8 in the middle sees four and needs two bridges to each. A 6 with three neighbours is full in the same way. A 4 in a corner sees only two neighbours and needs both doubled.
Odd numbers help too. A 5 with three neighbours cannot reach five with only two of them, so each neighbour gets at least one bridge. A 3 in a corner gets at least one bridge in both directions.
Two islands of 1 next to each other may not be joined to each other: they would close off a pair, and the map must stay connected. The same goes for two 2s joined by a double bridge. This isolation rule decides many of the harder medium grids.
Work in passes. Mark what is certain, then look again at the islands whose neighbours just filled up.
Undo, hints and saving
Every bridge goes into the history, so undo and redo can take you back to any point of the solve. If the board already holds a mistake, the hint points at it before it suggests anything new. The grid is saved as you play: close the page and it opens again with your bridges in place, and the win screen shows your time, hints and best time for that difficulty.
Questions
Is there always only one solution?
Yes. Every grid on the site is checked when it is built so that exactly one set of bridges fits all the numbers.
What makes hard grids hard?
Easy grids fall to counting alone. Medium ones need the isolation rule, and hard ones sometimes need you to try a bridge one step ahead and see that it breaks something.
Where are more Bridges puzzles?
There are 42 numbered Bridges puzzles in easy, medium and hard, each on its own page, and Bridges often turns up as the Puzzle lamp of today's strand.
How do I remove a bridge?
Tap the water between the two islands until it is empty again, or drag across the same pair to change it. Undo works too.