HASHI · BRIDGES · VERIFIED UNIQUE SOLUTIONHashi puzzle online
Build one connected bridge network between numbered islands. Every island must receive exactly its clue number of bridge ends, only nearest visible islands can connect, each pair can carry one or two bridges, and bridge paths may never cross.
What makes Hashi different
Hashi, also known as Bridges or Hashiwokakero, is not a fill-every-cell puzzle. The numbers are islands and the meaningful space is the network between them. A clue of 3 might be satisfied by three single bridges, or by one single and one double bridge, but only if those paths lead to the nearest visible islands in the same row or column.
The local arithmetic is only half the puzzle. A bridge arrangement can satisfy every number and still be wrong if it splits the board into disconnected groups. Whole-board connectivity is why strong Hashi solving alternates between local degree arithmetic and global network reasoning.
Verified rather than assumed
V0.102 freezes 45 source puzzles across 7×7, 8×8 and 9×9 boards with Easy, Medium and Hard pools. Each source is recounted by an independent exact solver that enforces island degree, one-or-two bridge multiplicity, crossing exclusions and final connectivity at the same time.
Every source is also checked through all eight square symmetries, giving 360 verified playable variants. A deterministic URL seed chooses a source and symmetry, so reopening the same Practice URL reconstructs the same board for QA, sharing and replay.
How to play Hashi
Start by looking at islands whose number is close to the maximum number of bridge ends they could still accept. A corner island with only two possible neighbors can force capacity quickly. An island showing 4 with two visible neighbors must use two bridges in each direction. An island showing 3 with two neighbors needs at least one bridge in each direction and one of those directions must be doubled.
Only the nearest visible island in each orthogonal direction is a candidate. You cannot jump over an island to reach a farther one. Use Single for one bridge, Double for two parallel bridges and Remove to clear a candidate connection. The small count beside every island shows its current bridge total so you can compare it with the clue without recounting the board manually.
Crossings are illegal. If a horizontal route and a vertical route pass through the same empty point, at most one of those candidate connections can be active. The board highlights crossing conflicts and overfilled islands, but a Clean run does not automatically reveal whether a non-conflicting choice belongs to the solution.
Connectivity is a first-class rule
Do not wait until the final move to think about connectivity. If a cluster of islands has only one remaining route to the rest of the board, that route may be forced even when local clue counts leave alternatives. Conversely, finishing all numbers inside a small closed group can be a trap if it disconnects that group from everything else.
A useful habit is to scan for narrow cuts: places where only one or two candidate connections can join large regions. Hashi becomes much easier when you treat those cuts as seriously as the island numbers.
Easy, Medium and Hard pools
The three pools vary island density, extra network cycles and the share of double bridges. Easy boards expose more direct degree deductions. Medium boards create more competing routes. Hard boards contain denser candidate networks where crossing restrictions and connectivity deductions matter earlier.
Difficulty is a product label, not an IQ score or percentile. The site stores only local move and time records plus specialist streak information in the browser.
Tools that preserve the reasoning loop
Hint places one verified bridge state when you are stuck. Check summarizes crossings, overfilled islands and remaining disagreement with the verified solution. Undo and Redo restore exact prior snapshots, while Restart returns the current deterministic board to its opening state. Using Hint, Check, Undo, Redo or Restart marks the run Assisted so Clean records remain comparable.
Autosave stores bridge states locally. A same-seed Practice URL restores the same source, symmetry and progress. Fresh Practice creates a new seed. Share copies a concise puzzle summary without uploading the board to a server.
Bridge arithmetic that scales
Hashi deductions often begin with capacity. If an island has two possible neighbors, those directions can hold at most four bridge ends in total. A clue of 4 therefore forces both directions to be double bridges. A clue of 3 means at least one direction is double. Similar minimum-capacity reasoning works around three- and four-neighbor islands and can eliminate impossible bridge counts before any global reasoning is needed.
After placing a bridge, recalculate the remaining capacity of both islands. A single local move changes two clues at once and can create a cascade of forced multiplicities elsewhere on the board.
Crossings provide negative information
A potential bridge does not need to be numerically impossible to be eliminated. If activating it would cross a bridge that has already become forced, the crossing candidate must stay empty. This geometric exclusion can simplify a dense board because a forced path may remove several orthogonal options at once.
The game renders every candidate connection with a generous hit area but draws only the active single or double lines, so geometry stays readable on mobile without making the actual paths artificially thick.
Connectivity deductions before the finish
Suppose a nearly completed group of islands has exactly one candidate route to the rest of the puzzle. Even if the island numbers inside that group can be satisfied without the route, closing the group would violate the connected-network rule. The external route must remain available and may become forced. This cut reasoning is a defining Hashi skill and is independently checked by the exact solver.
The verifier does not accept locally satisfied island numbers unless every active bridge belongs to one connected component spanning all islands. That prevents the common false positive where two separate perfect-looking subnetworks are mistakenly counted as solved.
Practice without an account
Practice is unlimited and browser-local. Choose 7×7, 8×8 or 9×9 and Easy, Medium or Hard, then keep the URL if you want a reproducible board. Nothing in this specialist changes the site’s Today’s 6 rotation. The frozen bank and deterministic selection make the game suitable for offline-first use through the same PWA shell.
Daily Hashi
Daily mode maps the calendar date to a stable size, difficulty, source and symmetry. Everyone using the same build and date gets the same deterministic specification. Daily Hashi keeps its own local history and streak separate from the main Today’s 6.
Read the Daily Hashi guide or open the game directly and switch between recent dates with the day controls.
Rules checklist
Every island ends with exactly its printed number of bridge ends. Candidate bridges are horizontal or vertical and reach only the next visible island. A pair of islands may have at most two bridges. Bridge paths never cross. Finally, every island must belong to one connected network. All five conditions are enforced by the independent verifier before a frozen source enters the release.