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Module 4 · IntermediateLesson 18 of 28

Intermediate Practice

Choose and apply intermediate eliminations without technique labels, then use the resulting simpler deductions to continue.

Outcome

You can look at an unlabeled candidate grid, choose a productive search mode, apply an intermediate elimination, and return to simpler deductions afterward.

Intro copy

Real puzzles do not say:

“Use a Hidden Pair now.”

The skill you need is earlier:

What kind of structure is this grid giving me?

Intermediate Practice removes the labels and trains that decision.

Step 1 — Choose a search lens

Three optional tools appear.

Unit view

Which row, column, or box is most constrained?

Useful for:

  • Singles;
  • subsets.

Digit view

Where can this digit go?

Useful for:

  • Hidden Singles;
  • Locked Candidates;
  • Hidden subsets.

Cell view

Which cells have small or related candidate sets?

Useful for:

  • Naked Pairs;
  • Naked Triples.

The learner chooses a lens. The UI does not automatically reveal the technique.

Step 2 — Guided cascade

Required state: A validated sequence where:

  1. Pointing creates an elimination;
  2. the elimination exposes a Naked Pair;
  3. the pair creates a Single.

Move 1

Prompt:

No direct placement is available. Try a digit-first search.

Hint ladder:

  1. choose candidate 7;
  2. inspect one box;
  3. notice all source 7s share one row.

Learner performs Pointing.

Feedback:

Good. Now stop searching for advanced patterns. What changed?

Move 2

The affected row now contains two matching bivalue cells.

Learner identifies Naked Pair.

Feedback:

The candidate elimination exposed a two-cell reservation.

Move 3

Pair elimination creates a Naked Single.

Learner places it.

Completion copy:

This is the intermediate loop: eliminate → simplify → return to direct logic.

Step 3 — Unlabeled Claiming

No source unit highlighted.

Prompt:

Find one logically forced candidate elimination.

Optional Hint 1:

Follow one digit through a row.

Optional Hint 2:

All of its positions fall inside one box.

Only after the correct move:

This was Claiming / Box-Line Reduction.

Technique names become feedback, not instructions.

Step 4 — Unlabeled Hidden Pair

Prompt:

Two digits in this unit are running out of places.

No cells highlighted.

The learner uses candidate filters and cleans the pair.

After success:

This was a Hidden Pair. You found it digit-first.

Step 5 — Unlabeled Naked Triple

Prompt:

Three small candidate cells in this unit reserve a complete set of digits.

Learner selects cells and sees the union only after selection.

After success:

This was a Naked Triple. You found it cell-first.

Step 6 — Nothing advanced needed

Show a candidate grid containing a Hidden Single plus a tempting Pair-like structure.

Prompt:

Find the simplest useful move.

Correct answer: Hidden Single.

Feedback:

Good. Intermediate solving is not a contest to use an intermediate technique. Take the simplest forced progress first.

This is important enough to test directly.

Repeatable Practice

Technique pool:

  • Hidden Single;
  • Pointing;
  • Claiming;
  • Naked Pair;
  • Hidden Pair;
  • Naked Triple;
  • Hidden Triple.

Difficulty progression:

Assisted

  • useful unit highlighted;
  • candidate filter suggested.

Guided

  • family-level hint only.

Independent

  • full candidate state;
  • no pre-highlighting.

Distractor

  • several real patterns exist;
  • learner is rewarded for choosing a simple productive deduction.

Global hint ladder

Hint 1 — Search mode

Try digit-first.

or:

Try cell-first.

Hint 2 — Area

Highlight the useful unit.

Hint 3 — Structure

One digit is confined to an intersection.

or:

Two digits share the same two cells.

Hint 4 — Family

Name Locked Candidates / subset.

Hint 5 — Technique

Name exact technique.

Hint 6 — Visual reveal

Highlight source and valid elimination targets.

This ladder is a reusable design pattern for later Advanced Practice.

Final checkpoint

Required construction:

  • short validated puzzle segment;
  • at least two intermediate eliminations from different families;
  • at least two simpler follow-up deductions;
  • more than one visually plausible search direction.

The learner solves 6–10 moves without technique names appearing before the move.

After each deduction, the UI can label it:

Pointing
Naked Pair
Hidden Single

This reinforces vocabulary after recognition rather than using vocabulary as a crutch.

Completion

Complete:

  • guided cascade;
  • three unlabeled intermediate states;
  • simplest-useful-move test;
  • final checkpoint segment.

Completion copy

You can now make progress when direct placements stop.
The next layer connects candidate patterns across larger parts of the grid.

Actions:

Next

X-Wing

Fish expand the search beyond one unit or intersection and follow one digit across multiple rows and columns.

Reference

Read Intermediate Sudoku Strategies when you want the complete search order rather than one specific technique.