An empty mark is useful information.
A × is not a second kind of blank. It records a conclusion that the cell must stay empty.
Use × for a proven empty cell. Use an untouched cell for something you have not determined yet.
Unknown and empty are different
At the start, an untouched cell may eventually be black or empty. Marking it with × removes the black possibility. That can be just as helpful as filling a black cell, but the mark needs a reason.
For example, a five-cell line with a single clue of 2 already has black cells at positions 2 and 3. The only allowed group is complete. Cells 1, 4 and 5 must be empty: adding another black cell would extend the group or create an extra group.
Clues: 2
| Arrangement | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|
| Given | unknown | black | black | unknown | unknown |
| Finished | empty | black | black | empty | empty |
Separate groups, not individual cells
Clues 2 1 mean a group of two consecutive black cells followed by a separate single black cell. There must be at least one empty cell between those groups. The separator can be longer than one cell if the line has room.
A × does not have to appear before the first group or after the last group. A black group is allowed to touch the edge. Do not invent a border of empty cells around the puzzle.
Use an empty cell to divide the possibilities
A black run cannot cross a cell that is definitely empty. If a run is too long for the spaces on one side of that mark, those positions cannot hold it. Combine this with the order of all the clues before assigning a group to either side.
Be careful when only part of a group is known. Two black cells next to each other do not automatically finish a clue of 3. Marking both ends too early would prevent that group from ever reaching its required length.
On Nonogram0
Select Mark to place ×. Select Erase to take a mark back to unknown. One drag is one undo, so a row of mistaken marks can be reversed together.
The game accepts a correctly filled black pattern without requiring an × in every white cell. Empty marks are there to support your reasoning, not to add busywork before completion. A rule check finding no conflict is not a guarantee that each mark is correct.
Try three small deductions
These are practice lines, not a saved game. Fill only what is certain; leave anything uncertain unknown.
Close a finished run
The two black cells are already fixed. Mark the cells that must now be empty.
Clues: 2