Daily Hashiwokakero
The rule
Join the islands with bridges until every number has that many bridge ends, and the whole thing is one connected network.
Bridges run straight across or down between two islands. At most two between any pair. They may not cross each other, and they may not pass over an island.
Tap one island then another to lay a bridge. Tap the same pair again for a double, and once more to take it away. An island goes dark when its count is met.
Where to start
Look for islands whose number leaves them no choice. An island on a corner with only two neighbours and a 4 must send a double bridge to each. A 3 with two neighbours needs at least one of each, so both of those bridges are certain even before you know which carries the second.
The connection rule does real work too. If a group of islands has finished all its numbers among themselves but the rest of the board is not attached to it, that arrangement is wrong however neat it looks.
In your hands
Untangling something that has to come apart in one piece is the same pleasure as a brain teaser.
Solvable Without Guessing
Every board here was built by laying down a network of bridges first and reading the numbers off it, so an answer is guaranteed before anything else happens. Then two separate questions get asked, and keeping them apart matters more than it sounds. The first is whether the numbers admit only one network, which is settled by counting them. The second is whether a solver that only makes forced moves can get there. A puzzle has to pass both, and roughly one network in five does.
The move that does most of the work is a bound rather than a certainty: if every other bridge at an island were doubled and the total still fell short, the remaining bridge has to make up the difference. Without that one rule almost nothing on a Hashiwokakero board is deducible at all.
More to Play
There are twenty four daily sudoku variants, a kakuro, a slitherlink, a shikaku and a pentomino board. For puzzles you can hold, see mechanical puzzles.
If you like a puzzle that yields to patience rather than luck, that is exactly what a good interlocking puzzle asks of you. See the 6 Piece Cross, or the rest of the collection.
Frequently Asked Questions
How do you play Hashiwokakero?
Join the islands with bridges until every number has that many bridge ends, and the whole thing is one connected network.
Is Hashiwokakero free to play?
Yes. There is a new hashiwokakero here every day, free, with no account and nothing to install. It plays in the browser on a phone or a computer, and it remembers where you got to.
Can every puzzle be solved?
Yes. Every puzzle is handed to a solver that may only use techniques a person can use, and anything it cannot finish is thrown away rather than published. You never have to guess.