Play a free pencil-and-paper puzzle: draw one closed loop through a grid of dots so every number counts its sides correctly. Six sizes, three levels.
Time 0:00
Numbers met 0
Your best -
This board is wider than the space on this screen, so it is at its smallest tap size. Scroll the board sideways to reach the rest.
Draw one closed loop along the grid lines. It may not branch or cross itself. A number says how many of that cell's four sides the loop uses. Tap close to an edge to draw it, tap again to remove it. Keyboard: arrow keys move between dots, Shift plus an arrow draws or erases the line to the next dot, Space switches the pen on or off so plain arrows draw, L and X choose line or cross, U undoes, H gives a hint. Hint, Check and Show answer count as help, so the puzzle will not set a best time.
Each puzzle starts from a random shape whose outline is one loop. The numbers are read off that loop, then removed one at a time. A number is only removed if a solver can still prove the loop is the one and only answer. That is why Hard has the fewest numbers.
On Easy the puzzle is also checked so that simple deductions are enough: a number that already has all its lines, a dot that has two lines, a dot with one line and one place to go. No guessing is ever needed.
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The board is a grid of dots with numbers in some of the cells. Draw one closed loop along the lines between neighbouring dots. The loop may not branch, cross itself or touch itself, and it must come back to where it started. A number in a cell says how many of that cell’s four sides the loop uses. A cell with no number can have any count, including zero.
Tap close to an edge to draw it, and tap again to remove it. The tap goes to whichever side of the cell under your finger is nearest, so you do not have to hit a thin line. Choose Mark X to put a small cross on an edge you know is not part of the loop. A right click, or a Shift click, uses the other mode for that one tap. Undo steps back one mark at a time.
When the loop is closed and every number is met, the loop pulses and the puzzle is solved.
Every state has a shape as well as a colour.
Click or tab onto the board. The arrow keys move a ring between dots. Hold Shift with an arrow to draw or erase the line to the next dot and move there. Press Space to put the pen down, so plain arrows draw, and press it again to lift it. L and X choose line or cross, U undoes and H gives a hint. Every move is read out: the dot you are on, its row and column, the numbers around it with how many lines they have so far, and whether a number just became complete.
Press Hint and the game looks at the numbers and the marks you have already made. If one of your marks is wrong it points at that. If something follows from the numbers it points at that edge and says whether it must be a line or empty. Only when nothing is forced does it simply reveal a line of the answer. Check my lines marks every wrong mark and Show answer draws the loop. All three count as help, and a puzzle where you used help does not set a best time.
Making a puzzle. The generator grows a random blob of cells one cell at a time. A cell is only added if the blob stays in one piece, has no hole, and has no spot where two corners touch, because any of those would make the outline more than one simple loop. The outline of the blob is the answer. Reading off how many sides of each cell are on the outline gives a full set of numbers.
Keeping the answer unique. The numbers are then removed in random order. After each removal the solver counts solutions, stopping at two. If there is still exactly one, the number stays removed; otherwise it goes back. A check that takes too long also counts as “not unique”, so the puzzle is never less certain than it claims.
The solver. It repeats a few local rules until nothing changes: a cell whose lines are all placed takes no more, a cell that needs every remaining side takes them all, a dot has either no lines or two, and a dot with one line and one place left must use it. It also notices when a finished loop appears alongside other lines, which is a dead end. When the rules stall it guesses one edge and tries both ways. Easy puzzles are the ones where the rules never stall.
Nothing is uploaded and there is no account. Your best time for each size and level is saved in your browser as a small whole number of seconds inside a small JSON object. Clearing site data removes it.
For informational purposes only. Not financial, medical, or legal advice. You are solely responsible for how you use these tools.