How to play Bridgework

Join the numbered islands into one network. Every board has exactly one answer and can be reasoned out in full — there is never a guess to make.

Play Bridgework free → More puzzle games

Bridges — also called Hashiwokakero, and sometimes Hashi — is a pure deduction puzzle. There is no luck in it, no hidden information, and in this version no guessing either. Everything below is a consequence of four rules and one guarantee.

The four rules

Every island carries a number from 1 to 8. That number is the count of bridge ends touching it when the board is finished — not the number of neighbours it joins, which is why an 8 can be reached with only four neighbours and a 2 might be one neighbour joined twice.

Bridges run only horizontally or vertically, only between two islands with a clear line between them. A bridge cannot pass through an island, and no island is ever placed directly beside another, so every bridge has room to exist.

Any pair of islands may be joined once or twice, and never three times.

No two bridges may cross. A horizontal span and a vertical span that would intersect are mutually exclusive; whichever you build first shuts the other out until you clear it.

The fifth rule, which is really the puzzle

When the board is done, every island must be reachable from every other. One network, not several.

This is easy to say and easy to forget, and it is the difference between a board that looks complete and one that is. You can meet every single number on the board and still be wrong, because you have built two separate rings that never touch. On the smaller boards this rarely comes up — meet all the numbers and the network usually joins itself. From the Hard band up it is a live constraint, and quite often the whole point of the last few bridges.

It also works as a tool rather than just a trap. If joining two islands would seal a small group off from the rest of the board with no way out, that bridge cannot be right, and ruling it out is frequently the deduction that unlocks a corner.

What the difficulty labels mean

Not grid size. Every board is rated by the hardest technique it actually forces you to use.

Easy and Medium boards are settled entirely by counting. Every step is of the form "this island needs 6, its neighbours can offer at most 6, so all of them are doubled", or "the other neighbours cannot cover this island's number between them, so this one takes at least one". Medium is not harder reasoning than Easy — it is the same reasoning across a bigger board.

Hard and Expert boards cannot be finished by counting alone. At some point you must assume a span carries a particular number of bridges, follow the consequences until something breaks — an island that can no longer reach its number, or a group of islands sealed off from the rest — and conclude the assumption was wrong. Expert boards need that manoeuvre several times over. It is still deduction, and the contradiction is always genuinely reachable; it is simply a step deeper than counting.

The guarantee

Two things are proved about every board before it is dealt to you. First, exactly one arrangement of bridges satisfies it. Second, a solver restricted to the techniques above can reach that arrangement. Any board failing either check is discarded.

So if you are stuck, something is deducible — you have not been handed a board that requires a coin flip, and there is no point in the puzzle where two answers remain and you have to pick.

Hints, undo and the daily crossing

A hint reads the board as you have actually left it. If what you have built so far is consistent with the answer, it finds the next forced bridge and tells you which island forces it and why. If you have built something that cannot be part of any solution, it says so and marks the offending spans instead — because no advice given on top of a mistake would be worth having.

Undo steps back one bridge and reset clears the board without changing the puzzle.

One crossing a day, the same for everybody. The week ramps: Monday and Tuesday are easy, Wednesday and Thursday medium, Friday and Saturday hard, and Sunday is an expert board. Solving extends your streak, solves finished without a single hint are counted separately, and the share text carries your time without giving anything away.

Controls

Drag from one island to another to build a bridge, or tap the two islands in turn. Repeating it adds a second bridge, and once more clears them.

Keyboard

Arrow keys build from the selected island.
Shift and an arrow moves the selection instead, Tab cycles islands.
Z undoes, H asks for a hint, R resets.

Strategy tips

Start with the islands whose number matches everything their neighbours could possibly give. An island showing 8 with four neighbours takes two bridges in every direction, and a 4 with only two neighbours doubles both. These cost no thought and open the board up.
A 1 and a 2 on the edge or in a corner are worth finding early — few neighbours means few possibilities.
When an island is nearly full, ask what the others cannot cover. If an island needs 5 and three of its four neighbours can supply at most 4 between them, the fourth takes at least one, whatever else happens.
Never join two 1s to each other unless they are the only islands on the board. They would satisfy each other and then sit there, sealed off from everything else forever.
Use the same logic on bigger groups. If a bridge would close off a pocket of islands with no remaining route to the rest of the board, it cannot be right — this is often the deduction that breaks a Hard board open.
Building a bridge shuts out every span that would cross it, so a bridge you are sure of tells you as much about the lines it blocks as about the islands it joins.
On Hard and Expert boards, when counting runs dry, pick a span with only two possibilities and follow one of them until something breaks. Assume, chase, contradict, rule out — the contradiction is always there to be found.
If you finish and an island is still not joined to the rest, do not start again from scratch. Every number is right, so the fix is a swap somewhere near the seam between your two networks.