Bridges is also called Hashiwokakero, or Hashi for short. The Japanese name means build bridges. It is the same puzzle with the same rules.
The rules
- Build bridges in straight lines, across or up and down, from one island to the next.
- A bridge always goes to the nearest island in that line. It cannot jump over an island.
- Each island needs as many bridges as its number.
- Two islands can have at most 2 bridges between them.
- A double bridge counts as 2 for both islands it joins.
- Bridges may never cross.
- In the end, all islands must be joined together.
The last rule matters. All numbers can be right while the islands still form two groups. The puzzle is only done when you can walk from any island to every other island over bridges.
These are the classic Hashiwokakero rules. Quirk uses square boards from 5 by 5 up to 10 by 10.
A worked example
This small board has 4 islands, one in each corner. The rest of the board is water, shown as a dot (·) in the table.
| Row | Left | Middle | Right |
|---|---|---|---|
| Top | 3 | · | 3 |
| Middle | · | · | · |
| Bottom | 1 | · | 1 |
- Look at the two 1s at the bottom. Each 1 can join the island above it or the other 1.
- If the two 1s join each other, both are full. They would be cut off from the two 3s. So no bridge goes between the 1s.
- Now the bottom left 1 can only reach the 3 above it. Build 1 bridge there.
- In the same way, build 1 bridge from the bottom right 1 to the 3 above it.
- The top left 3 now has 1 bridge and needs 2 more. Its only other neighbour is the top right 3. Build a double bridge between the two 3s.
- Check the top right 3. It has 2 bridges from the left and 1 from below, which makes 3.
- Every number matches and all 4 islands are joined. The puzzle is solved.
Here is a second, even smaller board. A 2 sits in the top left corner and a 3 in the top right corner. A 1 sits in the bottom right corner.
- The 2 has only one neighbour: the 3 to its right. Both of its bridges must go there, so build a double bridge.
- The 3 now has 2 bridges and needs 1 more. Its other neighbour is the 1 below it. Build 1 bridge there.
- The 1 is now full. Every number matches and all 3 islands are joined.
Beginner techniques
Islands with one neighbour
An island in a corner or at the edge often has only one neighbour. All its bridges must go to that neighbour. This is the easiest place to start.
Count what the neighbours can give
Each neighbour can give at most 2 bridges. A 4 with two neighbours needs 2 bridges to each. A 3 with two neighbours needs at least 1 bridge to each.
Also look at the neighbour's number. A neighbour with a 1 can only ever take 1 bridge.
A sure bridge blocks the way
Once you know a bridge must be there, nothing can cross it. Islands on both sides of it can no longer reach each other through that spot.
Do not close off a pair
Two neighbouring 1s cannot join each other when there are other islands. Two neighbouring 2s cannot share a double bridge for the same reason. They would form a small group that is cut off.
Find the only way out
Sometimes a group of islands has just one route to the other islands. A bridge must go there, or the group stays cut off.
Common mistakes
- Making every number right but leaving two separate groups.
- Trying to build a bridge that jumps over an island.
- Forgetting that a double bridge counts for both islands.
- Joining two 1s to each other while other islands still need them.
- Guessing early. Look for a bridge you are sure about first.
Questions
Is Bridges the same as Hashi?
Yes. Bridges, Hashi and Hashiwokakero are names for the same puzzle. Quirk uses the classic rules.
Does every puzzle have one solution?
Yes. Each Bridges puzzle in Quirk has exactly one answer. You can reach it by thinking it through, without guessing.
What sizes are there?
Quirk has square boards of 5 by 5, 7 by 7, 9 by 9 and 10 by 10. Bigger boards have more islands.
Can the bridges form a ring?
Yes. The islands may be joined in a ring. Only the numbers and the one joined network matter.
Why is my puzzle not finished when all numbers match?
The islands are in two or more groups. Quirk then shows a line under the board that says so. Look for a place where a group can link up with the rest.
Is Bridges good for beginners?
Yes. The rules are short and the small boards start easy. Quirk has hints, undo and reset when you get stuck.
Related puzzles
Playing it in Quirk
Tap 2 islands in turn, or drag from one to the other, to add a bridge. Do it again for a second bridge, and once more to remove both.
Quirk will not build a bridge that crosses another bridge. If an island gets too many bridges, tap the pair again to change them.
