Hashiwokakero,
one island chain.

Hashiwokakero — Japanese for 'build bridges' — is a logic puzzle invented by Nikoli. Numbered circles called islands sit on a grid, and you connect them with horizontal or vertical bridges. Each island's number tells you how many bridges must touch it. When every count is satisfied and all the islands form a single network, the puzzle is solved.

Click an island to select it. Click a second island in the same row or column to cycle the bridge between them: zero → one line → two lines → zero. Bridges cannot cross each other and cannot pass through another island. The board is solved when every island shows its required count and you can travel between any two islands by hopping along bridges.

Bridges run straight horizontally or vertically — never diagonally. Up to two bridges may connect any pair of islands. No bridge may cross another bridge or any other island. Every island must have exactly its number in incident bridges (1 to 8). All islands together must form one connected component.

Easy is a 7×7 board with about eight islands — a comfortable coffee break. Medium is 9×9, Hard jumps to 13×13, and Expert is 17×17 with around forty islands — the kind of evening project that pulls you in.

Start with the constrained islands: an 8 surrounded by four neighbours forces a double bridge in every direction; a 1 in a corner can only connect to the single available neighbour. After the forced moves, look at islands where the remaining bridge count equals the number of remaining directions — those directions all need at least one bridge. Always sanity-check connectivity: a group of islands that's already satisfied locally but isolated from the rest is a dead end.

Yes. Every "New puzzle" button click generates a fresh random board for the chosen difficulty. There is no daily limit, no streak counter — solve as many as you like.

Each puzzle is built by reverse construction. The generator places islands one at a time and grows bridges between them along open lines, recording the bridge plan as the canonical solution. The clue numbers are the bridge degrees at the end of construction, which guarantees the board is solvable.

Yes. Tap an island to select it, tap a second island in line to toggle the bridge. The board scales to the available width so puzzles stay tap-friendly on small screens — easy and medium are the most comfortable on phones; hard and expert play best on a tablet or laptop.

Each pair of islands cycles through zero → one → two → zero, so tapping the same two islands three times in a row returns the bridge to nothing. To wipe the board entirely, hit the Reset button on the toolbar.