How to Solve Hashi (Bridges): A Beginner’s Guide for Adults
To solve a Hashi (Bridges) puzzle, connect numbered islands with horizontal or vertical bridges so each island’s total equals its number. Start with the forced moves — islands that have only one possible direction — and each bridge you place reveals the next. It’s logic, not guessing.
What Is Hashi (Bridges)?
If you’ve stared at a grid of numbered circles without knowing where to begin, you’re not alone. “I see the circles but I don’t know where to start” is the most common thing beginners say about this puzzle.
Hashi — short for Hashiwokakero, a Japanese logic puzzle from the 1990s — goes by the name Bridges on many puzzle sites. The goal is simple: connect every numbered island so that all islands form a single connected group. The number on each island tells you exactly how many bridges must attach to it.
That’s the whole concept. Once the structure clicks, what looked like a guessing game turns into a satisfying chain of logical moves.
Quick vocabulary: each circle is an island, each connecting line is a bridge, and you win when every island has its correct bridge count and all islands are linked.
The Rules of Hashi (in Plain English)
According to Wikipedia’s article on Hashiwokakero, five rules define the puzzle:
- Each island’s number equals its total bridge count. A “3” island needs exactly three bridges attached.
- Bridges run horizontally or vertically only. No diagonal bridges.
- Two islands can share at most two bridges. You can build a single or double bridge between any pair — no triple.
- Bridges cannot cross. A bridge stops at any island it would otherwise pass through, and no two bridges may intersect.
- All islands must connect. When you’re done, every island must be reachable from every other island — one connected network, no isolated groups.
Quick worked example: a “3” island in the corner of a grid has two possible neighbors — one to the right, one below. The only way to reach a total of three bridges is a double bridge to one neighbor plus a single bridge to the other. The rules already narrow down where you can start.
Where Do You Start? Find the Forced Bridges
Those numbered circles aren’t a guessing game — every bridge can be worked out with simple logic, one forced move at a time.
A forced bridge is a bridge that has only one valid placement. Three situations always produce them:
An island with one possible neighbor. If a “1” island has only one other island it can reach, that single bridge is certain. Place it immediately.
An island whose neighbor count exactly matches its number. If a “4” island has exactly four accessible neighbors, it must build one bridge to each. All four are forced.
A “1” island near a wall. When only one direction is open, the bridge is automatic. Mark it and move on.
The power of forced moves is the chain reaction they start. One confirmed bridge changes what its neighbor needs, which may force the neighbor’s next bridge, which constrains another island — and progress builds from a single starting point.
Start with islands that have only one possible neighbor — that single bridge is confirmed. Place it, then watch how the neighbor’s options shrink. Each move reveals the next.
The High-Number Trick: Corners, Edges, and 7s & 8s
This is the move most beginners miss — and once you see it, it opens grids faster than any other technique.
The trick comes from counting how many neighbors an island can possibly have, then comparing that number to the island’s value.
Corner islands can reach at most two directions. This means:
- A corner “3” must build at least one bridge in each direction (the only way to reach 3 across two neighbors).
- A corner “4” must build exactly two bridges in each direction — all four are confirmed at once.
Edge islands (on a side, not a corner) can reach at most three directions. This means:
- An edge “5” must build at least one bridge in each available direction.
- An edge “6” must build exactly two in each direction — fully confirmed.
Any island in the grid can reach at most four directions. This means:
- A “7” island must build at least one bridge in every reachable direction.
- An “8” island must build exactly two bridges in every direction — the maximum possible, all confirmed.
Worked example: you find an “8” island with four reachable neighbors. Immediately draw two bridges to each neighbor. All eight bridges are forced with zero guesswork. The island is complete before you’ve made a single uncertain decision.
Conceptis Puzzles’ Hashi techniques guide describes this class of move as reasoning from “the maximum number of bridges that can be drawn” — once you know the ceiling, islands near it reveal their bridges automatically.
- Corner “4”, Edge “6”, or any “8”: all bridges confirmed.
- Corner “3”, Edge “5”, or any “7”: at least one bridge per direction confirmed.
Check position before anything else when a high-value island appears.
Stuck? Avoid Isolation, Cross-Reference, and Mark Done Islands
Every solver hits a point where no move looks obvious. Three tools get things moving again.
1. Avoid isolation. Ask: if I draw this bridge, does it permanently cut any island off from the rest of the grid? If completing one connection traps another island with no room to reach its required bridge count, that bridge is illegal — remove it from your options. This rule eliminates many candidate bridges that look valid at first glance.
2. Cross-reference. Look at an unsolved island and list what its neighbors need. If a neighbor is almost complete, only specific bridge counts remain available for the island in question. The intersection of what each island can give and what each neighbor can accept narrows the field quickly.
3. Mark completed islands. Draw an X through any island whose bridge count is exactly met. This is the most overlooked habit in Hashi. A “3” island with three bridges already placed cannot accept more — when you see it unmarked, you may accidentally try to add a bridge. One miscount cascades into wrong placements elsewhere. Mark done islands as done. It costs two seconds and prevents the most common source of errors.
As soon as an island’s bridge count is met, mark it done. Trying to add a bridge to a completed island is the most common Hashi mistake — a single miscount can invalidate several connected moves.
Getting Better at Hashi
The fastest way to improve is to start small. A 7×7 Hashi grid typically has fifteen to twenty islands and can be solved in a few minutes once forced-bridge logic is comfortable. Move to larger grids only after small ones feel routine.
The standard practice path: find a puzzle source — a Hashi app, a puzzle book, or a free printable — and work through one grid per day. The rules stay the same at every size; what grows is your ability to spot forced moves faster and apply the high-number trick at a glance.
If you enjoy this kind of step-by-step logic puzzle, the same reasoning style appears in other formats. How to solve Kakuro uses cross-referencing logic on a number grid. How to solve nonograms builds the same chain-of-forced-moves habit on a picture grid. And if you’re newer to logic puzzles generally, how to get better at Sudoku is the clearest entry point in the series.
Hashi is about connections and logical networks — not arithmetic. But if you enjoy the habit of quick number-logic between puzzles, Make 10 keeps that habit warm. It’s not a Hashi solver — it’s a different kind of puzzle where you connect tiles so their numbers add up to ten. No download, no account, plays in your browser in about thirty seconds to learn.
Is Hashi Based on Math or Logic? (Honest Answer)
Hashi uses no arithmetic. The numbers on islands are not values to add — they are counts of how many bridges attach. The required skill is spatial logic: tracking which connections are forced and what each placement tells you about its neighbors.
No fast math, no mental addition. If you can count to eight and reason through “this island has two neighbors, so the bridges must be split between them,” you have everything Hashi requires.
Just for fun — not medical advice.
Frequently Asked Questions
What is the goal of Hashi?
Connect all numbered islands with horizontal and vertical bridges so that every island has exactly as many bridges as its number, no two bridges cross, and the entire grid forms one connected network. The puzzle is solved when all five rules are satisfied simultaneously.
Can two islands share more than two bridges?
No. The maximum between any two islands is two bridges — one single and one double, or just a double. If an island needs more bridges than a single neighbor can supply, it must connect to multiple neighbors.
How do you know where to start a Hashi puzzle?
Look for forced moves first: islands with only one reachable neighbor, “1” islands with a single open direction, and high-value islands in corners or on edges. A corner “4” or any “8” island is fully confirmed before you reason through anything else.
What does a number like 8 mean in Hashi?
An “8” island needs eight bridges. Since any island can connect to at most four neighbors, an “8” must have exactly two bridges to each of its four reachable neighbors. All eight are confirmed immediately — the highest-value islands are the easiest to place.
Want a no-signup number puzzle to try right now? Make 10 is open in your browser.
More from the Make10s blog: how to solve nonograms · how to solve Kakuro · how to get better at Sudoku · brain games like Sudoku · all posts
Sources: Wikipedia — Hashiwokakero · Conceptis Puzzles — Hashi Techniques
Just for fun — not medical advice.