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Module 3 · CandidatesLesson 11 of 28

Pencil Marks

Use notes mode to record, remove, and interpret candidate digits without confusing notes with solved entries.

Outcome

You can use Notes to represent candidates accurately and choose between selective, full, or automatic candidate support.

Intro copy

Candidates are the logic. Notes are the interface you use to keep that logic visible.

This lesson is about using that interface without turning the grid into noise.

Step 1 — Explain the interface

Copy:

Notes do not solve a cell. They record possibilities you may need later.

Step 2 — Guided example

Target cell has candidate set {2, 5, 8} established by the previous lesson.

Prompt

Turn on Notes and record the candidates for this cell.

Hint 1

Add all three possibilities. Do not place a large solved digit yet.

Hint 2

The candidate set is 2, 5, and 8.

Correct feedback

Perfect. The cell is still unsolved, but its possibilities are now visible.

Incorrect feedback

That action placed a solved digit. Switch to Notes mode so you can record possibilities instead.

Step 3 — Try it

Exercise spec

Three cells with known candidate sets. User enters notes manually.

Then a correct digit is placed in a peer and one note becomes impossible.

Prompt:

Update the affected notes.

Correct feedback

Correct. Notes must match the current grid, not the grid from a few moves ago.

Incorrect feedback

One candidate is now blocked by the new solved digit. Remove it from every affected peer.

Step 4 — Practice

Include:

  • one selective-notes scenario where only a target digit is being tracked;
  • one full-candidate scenario;
  • one update that creates {7} and therefore a Naked Single.

Checkpoint

Give a small puzzle state and ask the learner to:

  1. enter complete candidates in one target cell;
  2. place a known solved digit in a peer;
  3. update the target notes;
  4. recognize if the target becomes a Single.

Completion

All note-entry tasks use Notes mode correctly; stale candidate removed; final transition interpreted correctly.

Next

Locked Candidates — use candidate positions across a box and line to make your first intermediate eliminations.

Reference

Read Sudoku Pencil Marks for selective vs full notation, automatic candidates, and common note-management mistakes.