Outcome
You can make your first forced placements by using missing digits and crossing constraints instead of guessing.
Intro copy
Time to solve something.
Start with a part of the grid that is almost complete. The fewer possibilities left, the easier it is to prove the next digit.
Step 1 — One missing digit
Required row:
1 2 3 4 5 6 7 _ 9
Prompt:
Which digit is missing?
Correct answer: 8
Correct feedback:
Good. The row needs every digit from 1 to 9, and 8 is the only one missing.
Incorrect feedback:
Compare the row with the digits 1–9. Which digit does not appear yet?
Step 2 — Check the whole cell
Use an example where a row is missing two digits, but the target cell's column or box rules one of them out.
Prompt:
This row still needs 3 and 7. Which one can go in the highlighted cell?
Guidance sequence:
- Show both missing digits.
- Highlight the relevant peer that blocks one digit.
- Let the learner place the remaining digit.
Step 3 — Try it
Three independent beginner states:
- one missing digit in a row
- one missing digit in a column
- two possible unit digits narrowed by an intersecting box/line
Checkpoint
Show a fresh grid state with no instructional highlight at first.
Prompt:
Find a cell you can solve now.
Hint 1:
Look for a row, column, or box that is almost complete.
Hint 2:
Highlight the relevant unit, but not the answer cell.
Correct feedback:
Nice. You used the existing digits to prove the placement instead of guessing.
Completion
Three guided placements + checkpoint solved.
Next
Scanning — learn how to find these opportunities across a larger part of the grid.
Reference
Read How to Play Sudoku and How to Solve Sudoku.