Hashi (Hashiwokakero) — Bridges Puzzle

Hashi, short for Hashiwokakero, is a bridges puzzle published by Nikoli in 1990. The Japanese name means “build bridges.” You get numbered islands and you join them with straight bridges. Nothing is hidden: every number is a fact, and a fair puzzle has one finished shape.

The rules are the whole game. People also look this up as a bridges puzzle, or as how to play Hashi. After the rules, this page covers the controls on the site and the first patterns worth learning by name.

Rules

An island shows a number from 1 to 8. That number is how many bridges must touch it. A single line counts as one. A double line, two strokes between the same pair, counts as two.

Bridges run horizontally or vertically between two islands that can see each other. They stay straight. They do not turn, and they do not pass through a third island. At most two bridges join one pair.

Bridges never cross. If a horizontal bridge and a vertical bridge would meet in open water, only one of those lines can be built.

Every island must end in one connected group. You can walk from any island to any other along the bridges. A loop is allowed. Closing a circle is not a mistake. A second group that never joins the first one is.

Each puzzle here has one solution. Two finished grids that both obeyed the numbers, the crossings, and the single group would not be a fair Hashi.

How to play on this site

Opening Hashi loads today’s daily puzzle, a 7×7 easy grid. The seed is the UTC date, so everyone who visits that day sees the same islands. A link can pin another grid: the address carries the size, the difficulty, and the seed. New game deals a fresh puzzle and writes that seed into the address, so the link you copy is the puzzle on the screen. Changing the size or the difficulty deals the same seed again at that setting.

Drag from an island to a neighbour in the same row or column to lay a bridge. Drag again and the single bridge becomes a double. A third drag clears it. Tap a bridge that is already drawn and it cycles through one line, two lines, and empty.

Select an island and the keyboard works. An arrow key adds one bridge toward the next island in that direction. Shift plus an arrow removes one. Undo and redo walk those moves. Hint places one bridge the rules already force, and names the idea: counting, an edge, or isolation. Check says the grid is unfinished, has a mistake, or is solved. Reset clears your bridges and keeps the islands. Print uses the browser. Download PDF builds a black and white copy of the puzzle on the screen. Packs, with the answer key at the back, are on the printable Hashi page.

Beginner strategies

Start with counting. Twice the number of neighbours is the most an island can hold, because each neighbour takes at most two. When the clue sits near that maximum, most links are already forced.

Corner 3 and corner 4. A corner has two directions. A 4 in the corner is a double both ways. A 3 needs three bridges across those two links, so each link has at least one. Draw those two singles. Which link is the double comes from the neighbour’s number.

Edge 5 and edge 6. An island on the side, not in a corner, has three directions, and three directions hold at most six bridges. A 6 is a double every way. A 5 leaves one bridge spare, so each direction gets at least a single. Draw the three singles and leave the extra bridge for a later count.

Center 7 and center 8. Four neighbours hold at most eight. An 8 fills every direction twice. A 7 uses every direction at least once, so draw four singles now. Three of those links still become doubles, depending on the islands around them.

Isolation. A cluster is full when every number inside it is met and no bridge leaves it. If another island is still outside, the grid is split, which the rules forbid. Do not seal a finished cluster off from an island that still needs a way in. The link that would close the group too early stays empty. The link that is the only way to keep an outside island attached has to be drawn. Easy grids, including the daily 7×7, mostly fall to counting plus the corner and edge patterns. Harder grids stay open until isolation says which bridge would strand an island.