Numberlink

How to play Numberlink (pipe-connecting logic puzzle)

Numberlink — sometimes called Flow, Pipe Link or Number Path — is a logic puzzle played on a square grid sprinkled with pairs of matching numbers. Your job is to draw a single unbroken path between every matching pair, moving only horizontally or vertically, so that no two paths ever cross or share a square. What makes a proper Numberlink puzzle satisfying rather than merely doable is the extra rule used here: your paths must cover every single square of the grid, with no square left empty and no square shared by two colours. That one requirement turns a puzzle with many possible connections into a puzzle with exactly one correct arrangement, so a wrong turn always shows itself as a contradiction and you can reason your way to the unique finish without ever needing to guess.

The goal

Connect every numbered pair with one continuous path of orthogonal steps — up, down, left or right, never diagonally — so that when you are done, all of the numbered pairs are joined and every square on the board belongs to exactly one path. The puzzle counts your time and keeps a running tally of mistakes, so the fastest, cleanest solve earns the best score.

The board and the numbers

The board is a square grid — 5×5 on Easy, 7×7 on Medium or 9×9 on Hard. Scattered across it are pairs of numbered cells: two cells marked "1" belong to the same colour, two cells marked "2" belong to another colour, and so on. Every generated puzzle uses a fresh set of colours sized to the board, so a hard puzzle can have well over a dozen numbers to connect rather than just a handful. Each pair of matching cells marks the two ends of one path; nothing else on the board is pre-filled, so the only cells with numbers printed on them are the endpoints you are trying to join.

Rules

• Every path moves one square at a time, horizontally or vertically — never diagonally, and never through a square already used by a different colour.
• Each numbered pair needs exactly one path connecting its two cells; a path may not branch, loop back on itself, or touch its own colour anywhere except along its own single unbroken line.
• When you finish, every square on the grid must be covered by exactly one path — there can be no empty squares and no square shared by two colours.
• Dragging into a cell already used by a different colour is rejected outright; the drag simply stops extending into that square.
• The puzzle is solved the instant every pair is connected and the whole grid is full — there is always exactly one arrangement of paths that satisfies every constraint at once.

Solving techniques

• Start from forced corners. A number sitting in a corner or hugging an edge often has only one or two directions it can possibly travel in, so trace those first — they anchor everything else.
• Watch for single-square gaps. When a stray empty square sits boxed in between already-drawn paths, whichever colour is nearest almost always has to be the one to fill it, since nothing else could reach it.
• Count the cells. Before committing to a long, winding route for one colour, estimate how many squares the remaining colours will need — if your route hogs squares another pair cannot possibly do without, back up and try a straighter line.
• Work from both ends. Extend a path a little from each of its two numbers and see where the two ends are forced to meet in the middle; this is often faster than committing to one direction all the way across the board.
• Never force a crossing. If two different colours seem to need the same square, that is a sign you routed one of them the long way around earlier — retrace and try a shorter path for that colour instead.

Controls

Press down on a numbered endpoint (or on any square that is already part of a drawn path) and drag across adjacent squares to extend that colour’s path. Dragging back over cells you have already drawn shortens the path — a classic retrace. A quick tap on any square that is part of a path, without dragging further, truncates that path back to the tapped square, a handy way to undo a wrong turn without dragging all the way back. Use New Puzzle at any time for a fresh randomly generated board, and the size selector to switch between the 5×5, 7×7 and 9×9 grids.

Daily challenge

Press Daily to load that day’s shared puzzle — everyone who plays on the same UTC calendar date gets the exact same grid, numbers and endpoints, so you can compare times and scores with friends on a level playing field. The date shown next to the Daily button is the UTC date the puzzle belongs to; a new daily puzzle appears automatically once the date rolls over.

Scoring and the leaderboard

Your score is calculated the instant the last path locks into place: score = 10000 − seconds×5 − mistakes×200, clamped so it can never drop below 1 or rise above 99,999. A fast, mistake-free solve is worth the full 10,000 points; every second you spend and every rejected illegal drag chips away at the total. Scores are recorded separately for each board size, so Easy, Medium and Hard each keep their own leaderboard and their own personal best.

Frequently asked questions