Explore the lesson’s lines
- Exact fit: five cells, clues 1, 3 — the required separator uses the last spare cell.
- Overlap: five cells, clue 3 — compare three possible placements.
- Crossing information: column 1 from the lesson — marks leave one legal arrangement.
- Uncertainty: five cells, clue 2 — four placements, no forced squares.
- Contradiction: an extra fill in cell 2 — no legal arrangement survives.
What the result means
A filled square is forced only when every surviving arrangement fills it. An empty square is forced when none fills it. A question mark means this line alone cannot decide. This tool does not inspect crossing clues or solve a whole board. A loaded lesson link includes its line length, clues and current marks; you can change them here.
Try a worked example
Keep length 7 and clue 5. The three arrangements share cells 3, 4 and 5, so those cells must be filled. Mark cell 1 empty; only two arrangements remain. Now cell 6 is filled in both of them as well.
Why there may be no patterns
A clue may not fit: 4, 4 needs nine cells after its required gap. Your marks may also contradict an otherwise valid clue. Zero patterns means the line is inconsistent; it does not automatically tell you which mark is wrong. Clear the marks to distinguish a clue that cannot fit from conflicting marks. Pattern calculations run in your browser. Editing the cells does not submit a form or send those edits to a server. Lesson links include their starting clues and marks in the page URL.
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