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Lizely

Numberlink Puzzle

Connect two pairs of matching numbers with continuous orthogonal paths while avoiding reused cells, overlaps, branches, and wrong endpoints.

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How to use

  1. 1.Move to an unused numbered endpoint with the arrow keys and press Space or Enter to start its path.
  2. 2.Extend the active line one orthogonal cell at a time, avoiding occupied cells and every nonmatching endpoint; Backspace undoes the route.
  3. 3.Connect both 1 endpoints and both 2 endpoints to finish, then use Restart to replay or Escape twice for the boss screen.

About Numberlink Puzzle

Numberlink Puzzle is a compact implementation of the standard Nikoli path-connection rules. A five by five board contains two cells labeled 1 and two cells labeled 2. Your task is to connect each matching pair with its own continuous line. Lines move through cell centers one orthogonal cell at a time, can turn at right angles, and may not reuse a cell. Separate lines cannot overlap, cross, or branch, and a route cannot terminate at the other pair's number.

This page deliberately follows the same-number-pair definition published by Nikoli and independently reproduced by the National Museum of Mathematics. A different game sometimes called Number Link asks players to connect 1, 2, 3, and later numbers in sequence with straight segments. That sequential variant is not used here. The endpoints, board size, simple two-pair layout, controls, and score are Lizely implementation choices; the pairing and path restrictions are the external puzzle rules.

Use the arrow keys to move the board cursor. When the cursor is on an unused numbered endpoint, press Space or Enter to begin that pair. While a pair is active, every arrow input attempts to extend its line by one cell. Reach the matching endpoint to finish the pair. Press Backspace while drawing to remove the most recent path cell, or press Backspace at the starting cell to cancel that unfinished route. When no route is active, the arrows move freely so you can select the next endpoint.

The fixed fixture is designed for a short, reproducible keyboard solve. Pair 1 occupies the top row and pair 2 occupies the bottom row. A clean solution draws four steps across the top, moves freely to either endpoint of pair 2, and draws four steps across the bottom. Eight path steps complete the board and earn 920 points from a starting value of 1,000. Only accepted path extensions count as moves; free cursor navigation does not reduce the score.

Contradictions are detected immediately. Trying to enter the wrong numbered endpoint reports that the route has reached another pair. Trying to enter any cell already occupied by either path reports a collision. Board edges stop the cursor rather than wrapping. Those states do not silently alter the line, so Backspace or a different direction can recover the active route. Completion freezes drawing and preserves the final result until Restart. Automated tests exercise orthogonal and diagonal movement, reused cells, overlapping paths, wrong endpoints, the four-endpoint invariant, and the full eight-step completion sequence.

The board is an accessible CSS grid. Every cell announces its position and whether it is an endpoint or part of a path. The selected cell has a visible outline. Paths, borders, surfaces, foregrounds, accents, and warnings use Lizely's site variables; there is no canvas, image asset, hard-coded palette, pointer-only gesture, or audio dependency. The complete game therefore works with a keyboard and remains readable under the site's active theme.

A completed best score may be stored only in this browser's localStorage under a game-specific key. It is not uploaded, attached to an account, or compared on a public leaderboard. Restart clears both paths, selection, active pair, contradictions, move count, and score. Press Escape twice within 400 milliseconds to show the shared simulated operations spreadsheet, then repeat the double press to restore the unchanged puzzle. Use Numberlink as a brief route-planning challenge, not as a measure of cognition. For more network logic, try Hashi Bridges, Hitori Puzzle, Tents Puzzle, or Pipes Puzzle.

Methodology & sources

The browser stores each pair as an ordered array of 5×5 cell indices. An arrow extension must have Manhattan distance one from the previous cell, remain in bounds, avoid every occupied path cell, and avoid nonmatching endpoints. Completion requires both arrays to begin and end on the two endpoints carrying their label with no reuse or overlap. Score is max(0, 1000 − 10×accepted path steps).

Frequently asked questions

Do I connect the numbers in sequence?
No. Standard Numberlink connects each pair of matching numbers. This board connects 1 to 1 and 2 to 2.
Can paths cross or share a cell?
No. Each cell can belong to at most one continuous path, and paths cannot cross, overlap, branch, or reuse a cell.
How do I undo a route?
Press Backspace while a path is active. It removes the last path cell, or cancels the route when only its starting endpoint remains.
Is the puzzle randomly generated?
No. This version uses a disclosed fixed 5 by 5 two-pair board for reproducible keyboard play and automated completion testing.

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