Clue Grid practice: solve the short-run challenge before opening the answers.
Try a new board with no run longer than three, record reasons for your marks, then compare three checkpoints and a complete ten-check solution.
Can you transfer the earlier lessons to a board that has no full-line clue and no run of four? This challenge uses several short runs in different orders. Counting three filled squares is not enough: a clue of 1 2 and a clue of 2 1 can force different positions.
Try the new board before opening the answers. Your task is to finish one consistent pattern and give a reason for each mark you place. The hidden checkpoints offer smaller pieces of help than the full solution. “Advanced practice” describes this exercise's place in the series; it is not a measured difficulty rating or a test of your ability.
Set up a clean attempt
Choose Practice this example in the side panel, or Load practice challenge below Clue Grid. Both load the short-run board with unknown squares and Edits at zero. Do not use New puzzle for this exercise: it generates different clues. Retry this board clears your marks while keeping these clues; refreshing this practice address also reloads the same starting puzzle.
Read rows R1–R5 from top to bottom and columns C1–C5 from left to right. Check that the displayed clues match this list before starting:
Rows Columns R1: 1 1 C1: 2 R2: 1 2 C2: 2 1 R3: 2 1 C3: 1 2 R4: 1 1 C4: 2 1 R5: 3 C5: 2
Use ■ for filled, × for an established empty square, and ? for undecided. An unknown square is not an empty note. Select Fill square or Mark empty, then tap a square or focus it and press Enter or Space. Repeating the same action clears the mark. The practice starts without supplied fills or automatic hints.
Attempt three checkpoints without the solution
- Find a first deduction: write all complete placements of column 2's clue 2 1. Which square is filled in every placement? Does that same evidence force the bottom square to be filled?
- Transfer the mark across: use your first fill in row 2, whose clue is 1 2. Determine that whole row. Explain why preserving only the total of three fills would not be a valid check.
- Finish and audit: continue using both directions. For every empty note, name the line that ruled it out. At the end, read the runs of all five columns, not just the rows that look finished.
On paper, keep a small ledger with these four entries per deduction: line, known marks, remaining placements, and newly forced cells. Do not count a repeated mark as new information. In the live game, reactivating an existing fill would remove it and change your edit count.
You can pause after a deduction, choose a different line, and still arrive at the same answer. The checkpoints and route below document one order. A different count is not automatically an error: edits record your actions, including corrections, rather than the amount of reasoning you did.
Open only the help you need
Checkpoint 1: compare all placements of column 2
A: × ■ ■ × ■ B: ■ ■ × × ■ C: ■ ■ × ■ ×
All three fill row 2, so R2C2 is justified. R5C2 is filled in A and B but empty in C. It is not forced by this column alone at the start. Do not choose between those alternatives yet. These are complete patterns, including the required gap between the run of two and the later single square.
Checkpoint 2: use the different run order in row 2
D: ■ × ■ ■ × E: ■ × × ■ ■ F: × ■ × ■ ■
R2C2 is filled. Only F retains it, so row 2 is × ■ × ■ ■. Mark R2C1 and R2C3 empty and fill R2C4 and R2C5. The single run must occur before the double run; using one of column 2's patterns just because it has three filled squares would reverse the row's clue order.
For the next push, inspect columns 1 and 3 using row 2's empty notes. You do not need to settle every unknown in either column to gain another forced fill.
Checkpoint 3: compare the board after the first five line checks
The full route's first five checks leave these marks. Open the route later if you need the reason for a particular cell. A ? is still undecided, even when a completed solution would eventually fill it.
× × ■ × ■ × ■ × ■ ■ ? ? ? ? ? ■ ? ■ ? ? ? ? ? ? ?
The new empty R1C2 rules out B and C in the first checkpoint, leaving only A in column 2. This now forces R3C2 and R5C2 filled and R4C2 empty. The bottom fill that was unsupported at the start has become justified by crossing evidence.
Compare a complete ten-check route
The route is hidden so you can attempt the challenge first. To replay its exact counts, start with Retry and activate only the listed new cells. Within a step, place all listed empty notes before its new fills. Change the Cell action choice as needed; selecting the action itself does not add an edit.
Reveal every deduction and the running edit count
- Column 2: fill R2C2. All three placements of 2 1 share it; other positions remain undecided. Edits: 1.
- Row 2: mark R2C1 and R2C3 empty; fill R2C4 and R2C5. Only pattern F retains the known C2 fill. Edits: 5.
- Column 1: mark R1C1 empty; fill R4C1. With R2C1 empty, the run of two can occupy rows 3–4 or 4–5. Row 4 is shared, while row 1 is empty in both. Edits: 7.
- Column 3: fill R1C3 and R4C3. R2C3 is empty, so the only 1 2 placements are ■ × ■ ■ × and ■ × × ■ ■. Both share these fills; R3C3 and R5C3 are still undecided. Edits: 9.
- Row 1: mark R1C2 and R1C4 empty; fill R1C5. The fill at C3 is one isolated square, C1 is empty, and C2 or C4 would extend the existing run. The second isolated fill must be C5. Edits: 12.
- Column 2: mark R4C2 empty; fill R3C2 and R5C2. R1C2 is empty, leaving only pattern A from the first checkpoint. Edits: 15.
- Column 4: mark R4C4 empty; fill R3C4 and R5C4. Its clue is also 2 1, with row 1 empty and row 2 filled, so only × ■ ■ × ■ fits. Edits: 18.
- Column 5: mark R3C5, R4C5, and R5C5 empty. Its run of two is already present at rows 1–2. Every lower square must be empty. Edits: 21.
- Row 3: mark R3C3 empty; fill R3C1. C2 and C4 are filled, while C5 is empty. With clue 2 1, C4 must be the final single and the double run must occupy C1–C2. Edits: 23.
- Row 5: mark R5C1 empty; fill R5C3. C2 and C4 are filled and C5 is empty, so the one run of three must occupy C2–C4. Edits: 25, and the board is complete.
Each of the twenty-five cells is marked once: thirteen fills and twelve empty notes. This documented order reaches its first win on the last fill. It is not a minimum-edit claim. The game checks the filled pattern for completion and does not require you to write every empty note.
Check the final answer in both directions
Reveal the complete pattern and column audit
× × ■ × ■ × ■ × ■ ■ ■ ■ × ■ × ■ × ■ × × × ■ ■ ■ ×
The five rows read 1 1, 1 2, 2 1, 1 1, and 3, matching the starting list. Read the columns top to bottom as a separate check:
- Column 1: × × ■ ■ × gives 2.
- Column 2: × ■ ■ × ■ gives 2 1.
- Column 3: ■ × × ■ ■ gives 1 2.
- Column 4: × ■ ■ × ■ gives 2 1.
- Column 5: ■ ■ × × × gives 2.
Check lines can report that current row and column patterns match. It does not certify the reason for an empty note or supply the candidate lists above. The final cross-check is a way to audit your written reasoning as well as the visible pattern.
Review the attempt rather than the number
If your board differs, compare one line at a time. Check clue order, mandatory separation, and whether you treated a ? as an established empty square. Use Undo last edit to inspect a recent change, or Retry to make a clean attempt. Both controls still work after a win; refreshing loses marks, edits, and undo history.
For another attempt on these same clues, write your own line order on paper and open only the checkpoint where you become stuck. Judge the explanation locally: a mark is justified when every remaining complete placement agrees. A successful replay does not prove the same method finishes every randomly generated puzzle, and a unique answer is not a promise about human difficulty.