Separate an annotation from a filled value
A cell can be unresolved even when you have written small candidate notes in it. Those notes describe possibilities you want to remember. They do not complete the cell, count as a correct answer, or change the rule that each row, column, and three-by-three box must contain 1 through 9 without repetition.
Check the selected cell and the current entry mode before tapping a digit. When notes mode is active, the action adds or removes an annotation. When actual-value entry is active, the digit is a proposed answer. The dedicated variant uses its own local saved state, so a note is not silently written into a separate classic Sudoku board you may also have open.
Build a candidate list from all three groups
For an empty editable cell, list the digits absent from its row, column, and box. A number already present in any of those groups cannot be a candidate. Keep the full list rather than only the two values that first caught your attention; missing an option can make a later elimination argument appear stronger than it is.
For example, suppose those three groups exclude 1, 2, 4, 6, 8, and 9 from a cell. The remaining possibilities are 3, 5, and 7. Record them as notes while leaving the answer unresolved. The example describes a candidate calculation, not a supplied complete puzzle or a promise that the first empty cell in your current board has those same options.
Revise notes after a new justified entry
A correct new value changes the restrictions in its row, column, and box. Revisit affected notes and remove candidates that are no longer possible. This variant provides manual notes; do not assume an automatic candidate generator will maintain every list for you after each change.
If you later undo a value or discover an earlier assumption was wrong, reconsider notes removed because of that assumption. A tidy-looking list can still be incomplete or based on an error. Use Clear or the notes controls according to whether you intend to remove an actual value or revise an annotation, and inspect the result before entering another number.
Test a candidate pattern before trusting its name
Suppose two cells in a row contain only the candidates 3 and 9. If those lists are complete and both cells truly have no other possibilities, the digits are reserved for those two locations, allowing elimination from other cells in the row. If one cell could also contain 5, the exclusive-pair argument does not hold.
The same caution applies to an X-Wing: four notes in a rectangle do not prove the required “only two locations” condition. There is no automatic X-Wing highlighting promised here. Manual notes help you retain a logical argument, but the argument must still be checked against the grid. An absent local conflict warning is not a guarantee that a proposed value belongs to the complete solution.
Preserve a useful record without treating it as proof
Undo can revisit prior actions, and the notes variant saves locally when browser storage is available and retained. A reload or return should be interpreted according to that stored state, not as a remote account backup. Clearing site data or changing browsers can remove access to the same notes.
You can pause with a cell still containing several candidates. That is an honest description of the unresolved problem. Before making a final entry, ask which visible constraints eliminated the other candidates and whether any earlier player values used in that reasoning remain uncertain. The goal is a readable, revisable record on mobile, not automatic solving, a medical benefit, or a promise that adding more pencil marks by itself will produce the next answer.
Frequently asked questions
Are candidates filled in automatically?
No. This variant provides manual notes that you add, remove, and review yourself.
Do notes count as an answer?
No. They record unresolved possibilities; an actual value is entered separately.
Does it detect X-Wings?
No automatic X-Wing detection or highlighting is promised.
Can I undo a notes action?
The variant includes undo for its recorded actions so you can revisit a change.
Are notes saved to an account?
No. They use the dedicated variant’s local browser storage when it is available and retained.