Shade Link for beginners: remove repeats and keep a connected path.
Learn three shading rules on a fixed four-by-four board, reproduce a complete answer, and test why side contact and an isolated unshaded corner fail.
Shade Link asks you to remove repeated numbers while protecting a connected set of unshaded cells. You change whether a cell counts; you do not change its printed number. A finished board must satisfy all three rules below at the same time.
- Among the unshaded cells, a number cannot appear twice in the same row or the same column.
- Two shaded cells cannot share a horizontal or vertical side. Shaded corners may touch.
- Every unshaded cell must be reachable from every other by horizontal or vertical steps through unshaded cells.
These are the common Hitori rules described by Nikoli in source [1]. Our boards, implementation and explanation are original work for this site; no affiliation or invention of the mechanic is claimed. This is a different task from adding numbers or dividing the grid into area rectangles.
Read what shading removes
If a row contains two unshaded fours, at least one must be shaded. You do not have to remove every four from the grid. Equal numbers can remain in different rows and different columns. You also do not have to leave one of every number in every row: this is a duplicate-removal puzzle, not a Latin-square completion task.
A shaded cell keeps a crossed-out printed number for reference, but that number does not count in duplicate checks. Every unshaded number counts, even if you have never touched its cell. You do not need to mark all sixteen cells as decided.
Control a cell, then ask for a check
Tap or click a numbered cell once to shade it; activate it again to unshade it. Each activation adds one toggle. A wrong assumption is allowed, so an accepted click is not a correct-answer signal. Press Check shading to see the three rule counts. Checking adds no toggle.
Use Tab to reach a cell and Enter or Space to toggle it. Arrow keys move focus to a side neighbour without changing the shading; they stop at the edge. Each cell's label gives its row, column, number and shaded state. A pressed cell is shaded, and the number is crossed out as well as recoloured.
A correct configuration does not lock merely because you made its last toggle. Press Check shading to finish. A successful check locks the cells and focuses Undo last toggle. You can then undo to inspect the preceding state or Retry this board to start again.
Load the exact beginner board
Choose Practice this example beside the article, or Load beginner board in the game. Check that Toggles is 0 and the four rows match. R and C mean row and column, starting at the top left.
4 1 4 3 1 4 4 2 3 2 1 1 4 2 2 1
Press Check shading before touching a cell. It reports 8 equal-number pairs, 0 shaded side pairs and 1 unshaded group, so the board is not solved. A pair means two currently counted equal numbers in one row or column; it is not a count of distinct values. For example, R1C1 conflicts with R1C3 in the row and R4C1 in the column. Those are two pairs involving one cell.
Reproduce a complete four-toggle answer
Retry first to compare a clean attempt. Activate only the four listed cells, once each, in this order. This is a checked route for learning the rules, not a claim that choosing any one member of a repeated pair will work. Each shaded cell remains shaded for the following steps.
- R1C1, number 4. This removes its row conflict with R1C3 and column conflict with R4C1. Toggles 1; six equal-number pairs remain.
- R2C3, number 4. This removes the conflicts with R2C2 and R1C3. Toggles 2; four equal-number pairs remain.
- R3C4, number 1. This removes the conflicts with R3C3 and R4C4. Toggles 3; two equal-number pairs remain.
- R4C2, number 2. This removes the conflicts with R4C3 and R3C2. Toggles 4; no equal-number pairs remain.
You may press Check shading after each step; those checks do not change the toggle count. At every listed checkpoint, shaded cells have no shared side and all unshaded cells remain one group. After the fourth toggle, press Check shading to register the win.
Reveal the finished map and all row and column checks
X denotes a shaded cell. The other entries are the unshaded numbers:
X 1 4 3 1 4 X 2 3 2 1 X 4 X 2 1
The remaining row lists are (1, 4, 3), (1, 4, 2), (3, 2, 1) and (4, 2, 1). The remaining column lists are (1, 3, 4), (1, 4, 2), (4, 1, 2) and (3, 2, 1). No list repeats a value. The four shaded cells share no sides. R2C3 and R3C4 do meet at a corner, which is allowed.
There are twelve unshaded cells, all connected by side steps. A route may turn; it does not have to be a straight row or column. The final check is 0 equal-number pairs, 0 shaded side pairs and 1 unshaded group. This printed board was independently checked for exactly one valid shading pattern. Four toggles describes the clean route above, not a general fixed number required by the rules.
See why two rule checks are not enough
Retry between the following experiments so each starts unshaded. They demonstrate failed conditions, not alternative solutions, and repeated numbers can remain too.
- Shade R1C1 and R1C2, then Check shading. These shaded cells share a side, producing 1 shaded side pair. Having fewer duplicate pairs does not excuse that conflict.
- Retry, then shade R1C2 and R2C1. These shaded cells only touch at a corner, so there are 0 shaded side pairs. Nevertheless, unshaded R1C1 is trapped: its only side neighbours are both shaded. The unshaded cells form 2 groups, so the board fails connectivity.
Reveal the experiment counts and Undo predictions
The side-touch experiment has 6 equal-number pairs, 1 shaded side pair and 1 unshaded group at Toggles 2. The isolated-corner experiment has 8 equal-number pairs, 0 shaded side pairs and 2 unshaded groups at Toggles 2. Neither wins. Shaded corner contact is allowed, but it does not guarantee a connected unshaded network.
Retry and complete the four-toggle route again. After a successful Check shading, Undo last toggle unshades R4C2 and returns to Toggles 3. Check shading now reports 2 equal-number pairs, 0 shaded side pairs and 1 unshaded group. R4C2 again conflicts with R3C2 and R4C3. A check was not an edit, so one Undo reverses the last toggle rather than a check.
Retry clears shading, check results and history while keeping the printed numbers. Undo restores only one earlier toggle. Toggling a shaded cell back also unshades it, but adds a new toggle instead of removing an old one.
Know what this first lesson establishes
The route shows how to check the three conditions on one example. It does not prove that a locally helpful shade is safe on a different board. Reducing duplicate pairs can create a forbidden shaded side or cut off an unshaded cell, so keep all three rules in view.
Load beginner board restores this exact example. New puzzle moves through a finite collection of 7 prepared boards and removes the practice parameter; the collection repeats. Refreshing a fixed practice address reloads its numbers with no saved attempt. Your choices remain in the browser tab; there is no account, payment, timer, leaderboard or required advertisement action. No health or measured ability benefit is promised.