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A little logic. A satisfying break.

How to play Hashi

Turn scattered islands into one connected network. Each number tells you exactly how many bridges meet that island.

Play Hashi

Already playing? Switch back to keep your board and Undo history. These examples are separate from your puzzle.

Degrees, crossings and one network

  1. Connect only the nearest visible island in a horizontal or vertical direction. Bridges cannot run diagonally, cross another bridge or pass through an island.
  2. A pair can have zero, one or two bridges. A double bridge counts twice toward both islands’ numbers.
  3. Match every island’s degree and connect all islands into one network. Separate complete groups do not solve the puzzle.

Worked examples

Before

After

Action: Add two bridges from the middle 4 to each neighboring 2. Each connection can hold at most two, so both must be double.

Use all the capacity

An island marked 4 with exactly two visible neighbors must have two bridges to each: each neighbor can take at most two. An island marked 3 with two neighbors needs at least one bridge to each, because the other can take at most two.

Rule out a crossing

Once a horizontal connection is known to need a bridge, any vertical connection crossing its interior must have zero bridges. That lost capacity can force another island to connect elsewhere. Merely drawing an unproved bridge is an assumption; a hint explains deductions conditional on your current entries.

Keep the network connected

Imagine two groups of islands with only one possible visible connection between them. That connection needs at least one bridge, even when local degrees alone leave it optional. Two separate pairs of 1 islands cannot each close off with a single bridge when there are other islands to reach.

Count a group’s boundary

Add the degree numbers inside a group. Each internal bridge contributes two to that sum; each bridge leaving the group contributes one. A group with an odd total needs an odd number of outgoing bridges, and every proper group needs at least one. This parity and the remaining capacity can force a bridge.

Checked techniques

Degree Capacity

An island’s remaining degree and available bridge capacities bound each connection.

Crossing Exclusion

A required bridge excludes every connection crossing it.

Connectivity Bridge

A component with only one possible exit must use that connection.

Builds on: Degree Capacity

Cut Degree Parity

The degree sum inside a cut constrains the parity of bridges crossing the cut.

Builds on: Degree Capacity

Controls & recovery

Ctrl+Z or Command+Z undoes the last edit or whole applied hint. Ctrl+Shift+Z or Command+Shift+Z redoes; Ctrl+Y also redoes. These work from the active board and its action buttons. Text fields keep their native editing shortcuts. Settings saves this game’s optional timer and Auto-check choice independently. Turn Auto-check off and use Check when you want to review your work.

Tap or click a numbered island, then a visible neighbor. Choose One bridge, Two bridges or Remove to set the connection. To start elsewhere, choose another island; Choose another neighbor keeps the first island. No dragging or precise line tapping is needed.

Tab reaches the board. Arrow keys move focus to visible neighbors, and Enter selects the focused island. Space cycles the selected connection 0 → 1 → 2 → 0 without changing its endpoints. With a pair selected, 1 and 2 set its count; 0, Delete or Backspace removes it. Escape cancels the neighbor selection. A solid outer ring marks the first island; a double ring marks its selected neighbor. Dashed lines show candidate neighbors; two parallel lines mean two bridges. Check explains crossings, overfilled degrees and disconnected complete groups.

Get a hint checks deductions from your current bridges. Dashed island outlines and the listed bounds explain the support; a marked connection is the action. Apply adds one bridge once, and Undo restores the prior board. Editing, canceling or changing puzzles invalidates the hint. Recheck means your current assumptions cannot satisfy the rules; it does not silently correct them.

Progress saves in this browser as you play. Your boards mixes all games in most-recently-played order. Share links and case-sensitive HSH1 and HSH2 codes reopen the original puzzle; downloads carry your bridges and timer. Restore asks before replacing progress. If another tab changes a saved copy, recovery keeps both versions available. Restart is undoable for bridges; it resets time and mistakes.

Two sizes, two offered levels

Choose 7 × 7 (the default) or 9 × 9, Easy or Hard. Easy uses degree capacity and crossing exclusion. Hard also uses global connectivity and cut-degree parity. The labels describe independently checked computational techniques, not measured human or publisher difficulty. Medium is unavailable for New; already-issued Medium HSH1 codes can still reopen under their original rules. Next from an issued Medium board opens the Hashi chooser, where you choose a size and Easy or Hard before creating a new puzzle.

Relaxed play has no mistake limit. Optional challenge play counts an added bridge beyond the puzzle’s answer as a mistake; an incomplete correct connection is not a mistake. The optional timer pauses when play is hidden or paused. New is finite: if creation reaches its limit or is canceled, your current board stays intact.

Hashi offers New, Next, saved and shared boards. Today’s Hashi and the published archive offer shared puzzles when available.