The loop cannot revisit any body cell in a Shingoki puzzle. Shingoki is a fixed-grid loop challenge that requires a single closed, non-branching orthogonal path drawn through every clue, and that constraint is enforced by the browser before the result is accepted. Every body cell on the route must appear exactly once; the only cell the route is allowed to touch twice is the starting clue, which is re-entered once at the very end to close the shape. Every accepted extension must move to an orthogonally adjacent cell that is not already in the route, and the only allowed duplicate is the starting cell on the final step. This rule applies equally to black and white circles, regardless of which direction the line passes through them. If you re-enter any other cell while drawing, the browser immediately rejects the move because a true single loop cannot self-intersect or branch. The rule is the same on the keyboard controls of the disclosed 4×4 fixture and on any other arrangement that follows the same Shingoki definition.
You can see the rule in action by opening the Shingoki Puzzle page and pressing Space or Enter on the black 6 in the upper-left cell to begin. From there, every accepted extension must move to an orthogonally adjacent cell that is not already part of the route, except at the very last step when the route returns to the start. Re-entering any other cell is treated as a self-intersection, and the browser flags the route as a dead end instead of letting the puzzle continue.
The No-Revisit Rule Explained
Shingoki is built around a single closed loop, not a path that wanders or a maze that branches. The route is stored internally as an ordered list of cell indices on the 4×4 grid, and each accepted movement appends exactly one new index to that list. The validator checks three things on every step: that the destination is orthogonally adjacent to the current cell, that the destination is not already in the list, and that pressing the boundary arrow does not push you off the board. If any of those checks fail, the move is ignored and the score does not change.
The closure rule is the only exception to the no-revisit policy. When the route finally returns to the index that started it, the validator accepts the duplicate because closing a loop means meeting your own starting point. A loop is not a path with two ends; it is one continuous path whose two ends happen to meet at the same cell. As soon as the closure is accepted, the validator then checks every clue on the board for shape and value coverage. If those checks also pass, the puzzle is solved. If any clue fails, the closed route is marked deadlocked rather than solved, which means the geometry was acceptable but a rule was broken elsewhere.
What Happens When You Try to Revisit a Cell
The browser rejects route reuse immediately. The moment you press an arrow key that would land on a cell already in your route, the move is refused and the cursor stays where it is. There is no warning dialog and no soft prompt: the input simply does nothing, and you keep drawing from your current position.
This rejection is what turns an accidental detour into a detected dead end. If you re-enter a path cell other than the start, the single loop would self-intersect or branch, which Shingoki does not allow. The validator recognises that your route has lost its single-loop property and marks the attempt as a dead end rather than as a regular mistake. A closed route with the wrong circle shape, value, clue coverage, or geometry is also marked deadlocked rather than solved, so the puzzle freezes the result until you restart.
Restart is the only way out of a deadlocked or dead-ended state. Pressing the Restart control resets the route to empty, restores the score to 1,000, and lets you begin again at any selected clue. Completion itself also freezes the result, so once a clean solve is accepted, the route and score stay locked until you deliberately restart. Board-edge arrows do nothing, so accidentally pressing an arrow while the cursor is on the perimeter simply costs you the move rather than the round.
How to Draw the Twelve-Step Perimeter Solve
- Press Space or Enter while the keyboard cursor is on the black 6 in the upper-left cell. This sets the start cell and arms the arrow controls for the route.
- Press the right arrow key three times to extend the route along the top edge of the grid, crossing the white 3 clue on the second cell.
- Press the down arrow key three times to extend the route down the right edge, reaching the bottom-right corner of the board.
- Press the left arrow key three times to extend the route along the bottom edge back toward the lower-left corner.
- Press the up arrow key three times to extend the route up the left edge and re-enter the starting cell, closing the loop.
- Watch the validator check both circles: the black clue at the start should turn on a corner, and the white clue should pass straight through. The score should drop from 1,000 to 880 once the clean solve is accepted.
The full perimeter route contains twelve unique body cells and takes exactly twelve accepted movements to close. A clean solve starts at 1,000 and subtracts 10 points per accepted step, so the final score is 1,000 − 10 × 12 = 880. Because every body cell on this route is unique and the route only revisits the starting cell for closure, the puzzle recognises the geometry as a valid single loop.
Why the Numbered Circles Reinforce the Rule
The single-loop rule is what makes the printed numbers on each circle meaningful. Every numbered clue adds a second condition on top of the shape rule: the combined lengths of the two straight arms that meet at that circle must equal the printed number. On the disclosed fixture, the black 6 sits in the upper-left corner of the perimeter route. Its two incident straight arms each run three cells along the edges of the grid, so 3 + 3 = 6, which is exactly the printed value. If you tried to revisit one of those arm cells to "fix" the path, the arms would no longer be straight, the value would no longer sum to 6, and the validator would refuse to close the puzzle as solved.
The white 3 sits one cell to the right of the black 6 on the same top edge. Its forward arm runs two cells along the top edge until it reaches the top-right corner, and its backward arm runs one cell back toward the starting black clue. The total of those two arms is 2 + 1 = 3, matching the printed number. A route that revisited the white 3 itself would never reach the corner on one side and the black clue on the other, so the value condition would fail in addition to the no-revisit condition.
Both clue color and clue number must pass before completion is accepted. Even a perfectly closed loop will be marked deadlocked if it misses a clue, fails the black turn rule, breaks the white straight rule, or returns the wrong summed value at any numbered circle. This is why every body cell matters: each unique cell you visit carries the arms that build up to the printed totals, and revisiting a cell would corrupt the geometry that those totals depend on.
Comparing Shingoki to Other Loop and Path Puzzles
Shingoki sits in a family of puzzles whose defining feature is a single non-branching path, but each game applies the rule differently. The table below compares the no-revisit constraint across Shingoki and three of its closest neighbours.
| Puzzle | Path type | Cells revisited? | Source of constraint |
|---|---|---|---|
| Shingoki | One closed orthogonal loop | No body cells; start is revisited once for closure | Per Puzzle Shingoki FAQ |
| Masyu | One closed orthogonal loop through black and white pearls | No body cells; closure re-enters start once | Pearl turn and straight rules |
| Numberlink | Multiple open paths between matching endpoints | No cell reused across any path; paths may not cross or touch | Endpoint pair uniqueness |
| Pipes | Static tiles that form one connected network | Tiles stay fixed; looped networks are explicitly rejected | Single network without a closed sub-loop |
The pattern across these puzzles is that the no-revisit rule is usually driven by the geometry itself. A loop cannot self-intersect without becoming two loops or a branched shape. A path cannot share a cell with another path without either crossing or merging. Even static puzzles like Pipes forbid a closed network because a closed sub-loop would isolate the rest of the board from being connected. If you enjoy working through a Shingoki route and want a slightly different take on the same constraint, the Masyu Puzzle uses a similar closed loop with pearl-based turn rules, while the Numberlink Puzzle extends the no-revisit rule across several open paths at once.
Tips for Avoiding Accidental Revisits
The most common cause of an accidental revisit on the disclosed fixture is pressing an arrow that points back toward a cell you have already drawn through. Because the cursor announces its position, clue color and value, and path state on every cell, you can check before each move whether the cell in the direction you intend to press is already part of your route. If it is, the move will be refused, and that refusal is the validator telling you the single-loop property would be broken.
If you lose track of the route entirely, Restart restores the empty route and the full 1,000-point starting score. There is no penalty for restarting beyond the small amount of time you spend re-entering moves, and the disclosed fixture is short enough that a clean solve is reachable in twelve accepted movements. Double-press Escape opens the shared simulated spreadsheet boss screen and pressing it twice again returns you to the puzzle, so the keyboard controls stay available even if you need to step away mid-route.
For the full definition of the white-straight, black-turn, and numbered-length semantics, the maintained Puzzle Shingoki FAQ states the rule, and the ICLR 2026 PuzzleClone benchmark independently describes the same semantics in its rule summary.