Outcome
You can recognize a digit that is confined to a box-line intersection, decide whether the pattern is Pointing or Claiming, and remove the candidate from the correct outside cells.
Intro copy
Intermediate Sudoku introduces a new kind of progress:
You may know where a digit must live before you know its exact cell.
That regional certainty is enough to remove candidates.
Step 1 — Discover the two directions
Use the same box/row intersection for both demonstrations.
Pointing
Highlight a box.
Every possible 6 in the box lies on row 4.
Prompt:
We do not know which cell is 6. What do we know?
Expected idea:
The box's 6 must be somewhere on row 4.
Then extend the row outside the box.
Learner taps removable 6s.
Microcopy:
Box → line. The box points along row 4.
Claiming
Reset the same geometry.
Highlight row 4 instead.
Every possible 6 in the row lies inside one box.
Prompt:
What has row 4 claimed?
Expected idea:
Its 6 must be inside this box.
Learner removes 6 from the rest of the box.
Microcopy:
Line → box. The row claims the digit for the box.
Step 2 — Guided Pointing
Required state: A box contains exactly two candidate 7s in one row, with two outside eliminations.
Prompt 1
Select every possible 7 inside the highlighted box.
Incorrect feedback:
There is another legal 7 in the box. The pattern is not proven until you account for every source position.
Prompt 2
What do all of those positions share?
Correct target: row.
Prompt 3
Remove every 7 that the box now rules out.
Correct feedback:
Good. One of the source cells must be 7, so the rest of this row cannot contain 7.
Step 3 — Guided Claiming
Required state: A column contains all candidate 3s inside one box; the box has eliminable 3s outside the column.
Prompt:
Start from the highlighted column. Where must its 3 be placed?
Correct:
Inside this box.
Then:
Clear the candidates that can no longer be 3.
Incorrect feedback:
Stay with the source column. If its 3 must be inside this box, which 3s in the box become impossible?
Step 4 — Pair is not the rule
Present a Pointing example with three source candidates on the same row.
Prompt:
Does Pointing still work?
Correct answer: Yes.
Feedback:
Right. “Pointing Pair” is a common name, but the logic only requires every source candidate in the box to share one line.
This prevents the learner from memorizing “two cells” instead of the actual condition.
Step 5 — Near miss
Show a box with candidate 5 in:
- two cells on row 2;
- one additional cell on row 3.
Prompt:
Can you remove 5 from row 2 outside the box?
Correct answer: No.
Feedback:
No. The box can still place 5 on row 3, so its 5 is not locked to row 2.
Practice
Five controlled states:
- Pointing row;
- Pointing column;
- Claiming row;
- Claiming column;
- three-source Pointing or Claiming.
At least one near-miss should appear in repeatable practice.
Hint ladder
Hint 1
Follow one digit.
Hint 2
Check whether all of its positions in the source unit share the same intersection.
Hint 3
Decide which direction you are using: box → line or line → box.
Hint 4
Highlight the source unit and intersection only.
Final hint
Highlight the valid elimination cells.
Checkpoint
No direction label is shown.
Prompt:
Find one Locked Candidates elimination and explain the direction before making it.
Learner must:
- identify source unit;
- choose Pointing or Claiming;
- remove all valid candidates.
Completion
Complete:
- one Pointing row;
- one Pointing column;
- one Claiming row;
- one Claiming column;
- one three-source example;
- one near-miss rejection.
Next
Pointing Pairs
Now isolate box → line and build faster visual recognition.
Reference
Read Locked Candidates for the complete umbrella explanation and comparison with Singles/subsets.