How to play Mosaic

2One number

Read one number. A 0 clears its neighbourhood, including the numbered cell. A number that matches the neighbourhood shades every cell in it. A number that already has its shaded cells dots the rest. A number whose open cells are exactly what it still needs shades those cells.

A count of 0 Easy

A 0 has no shaded cell in its neighbourhood. Every open cell in that block is empty, including the 0 itself. The neighbourhood is the idea. The button writes all of the open cells in one press. On this figure the 0 is the edge at row 3, column 5. It looks at six cells: row 2 column 4, row 2 column 5, row 3 column 4, row 3 column 5, row 4 column 4, and row 4 column 5. The press dots all six. The 0 is one of the cells, so it takes a dot and it is lit.

A corner 0 looks at four cells. On a 6×6 easy grid the opening press dots the four cells of the corner 0 at row 1, column 6. That grid is not drawn. A 0 in the middle looks at nine. The second press on the grid in the next section dots nine cells around the 0 at row 4, column 2. That is the largest press of this sentence. It is not drawn. The smallest is two cells, later on another 5×5 easy grid. The button takes the earliest writable clue, so a later 0 waits. The grid in the next section opens on a 6, not on a 0.

A dot already on row 2, column 4 stays a dot. The press then writes the other five cells, and that first cell is not lit. That second picture is not drawn. The next press on this grid is another 0, on row 3 columns 1 and 2, row 4 columns 1 and 2, and row 5 columns 1 and 2.

The whole neighbourhood Easy

When the number equals the size of its neighbourhood, every cell in the block is shaded, including the numbered cell. A 4 in a corner, a 6 on an edge, and a 9 in the middle are the full blocks. The button writes every open cell of one number, then stops. On this figure the 6 at row 2, column 5 is an edge. It looks at row 1 column 4, row 1 column 5, row 2 column 4, row 2 column 5, row 3 column 4, and row 3 column 5. The press shades all six. The 6 is one of them, so the digit turns white on the violet, and the cell is lit.

This can be the first press. This grid has a 0, and the 6 is earlier in the scan, so the 6 runs first. The article still teaches the 0 before this, because that is the order the steps are tried. A later press of this same sentence can be one cell, once some of the neighbourhood is already shaded. The name stays "the whole neighbourhood", because the number still equals the size of the block. That one-cell press is not drawn. The largest press of this sentence is a 9. A 7×7 is not drawn for it.

Already enough Easy

Once the shaded cells already meet a number, every other open cell in that neighbourhood is empty. This is a count that has its shades, not a fresh 0. On this figure the 1 at row 1, column 6 is a corner. It looks at four cells, and row 2, column 5 is already shaded. The press dots row 1 column 5, row 1 column 6, and row 2 column 6. The known shade stays an ordinary violet cell. It is not lit. The 1 takes a dot, so it is lit.

The last press on this grid is a full neighbourhood and finishes the grid, so the live button skips that toast. This figure is the press before it. The toast shows. A 5×5 easy grid in this set never says this sentence, so the figure is 6×6. The smallest press of this sentence is one cell. The largest is eight. Neither is drawn.

Only one way left Easy

Count the open cells left in one neighbourhood. If that count is exactly what the number still needs, those cells are shaded. The open cells are the idea. The button writes all of them in one press. On this figure the 1 at row 1, column 1 is a corner. Three of its four cells are already dotted: row 1 column 2, row 2 column 1, and row 2 column 2. The last open cell is the 1 itself. The press shades it. The digit turns white. The three dots stay ordinary dots and are not lit.

This is not the first press. Three 0s run first. The article teaches the 0, the whole neighbourhood, and the met count before this. A one-cell press of this sentence can also be the press that finishes a grid. On one 5×5 medium grid that happens, and the toast is skipped. This figure is an earlier press. The toast shows. The largest press of this sentence is eight cells. It is not drawn. Two easy grids in this set never say this sentence. 5×5 and 6×6 easy do.

That is the end of the four easy sentences. Easy grids finish with these alone. The next section is the sentence medium grids add. The button hides that sentence on an easy label. A blank easy grid also never needs it.

3Two counts

Two nearby numbers can force the cells that sit in one neighbourhood and not the other. Medium grids use this. One press writes those cells. It can shade them, dot them, or mark both sides. The shared cells stay blank.

In one neighbourhood only Medium

Look at two numbers that sit within two steps of each other, counting a diagonal as one step. The cells that belong to one neighbourhood and not the other have to make up the difference in the counts. When those cells are exactly the extra shades, they are shaded. When the difference is already met, they are empty. One press writes every such cell, on one side or on both. The cells the two numbers share stay blank. Hint lights the cells it writes. On this figure it does not light either number.

The 4 at row 2, column 4 and the 1 at row 2, column 5 share a side. The 1's neighbourhood sits inside the 4's. The three cells that belong only to the 4 are row 1 column 3, row 2 column 3, and row 3 column 3. The 4 needs three more shaded cells than the 1, so those three are shaded. The shared cells wait. Neither number is written. A dot in any of those three would leave the 4 short once the shared cells have matched the 1.

The same sentence can leave the extra cells empty. On another 5×5 medium grid, two 3s that share a side dot two cells and shade nothing. That grid is not drawn. One press can also mark both sides at once. On another 5×5 medium grid the opening press dots two cells and shades seven, and the two numbers are two steps apart, which is as far as the button looks. That grid is not drawn. Easy grids in this set finish without this sentence. A medium grid needs it because the one-number sentences stop. A medium grid can still open on a 0. This one opens on the pair. The smallest press is one cell. The largest is thirteen. Neither is drawn.

4What if one cell

A hard grid can still have one blank where you try both marks. The mark that cannot be finished is dropped. Sometimes both marks can be finished, and they force the same cells somewhere else. Hint writes those cells and leaves the cell you tried blank.

Shading it fails Hard

The sentences above write a cell because a number, or a pair of numbers, already forces it. A hard grid can still have one blank where both marks have to be tried. Shade this cell, and the counts cannot be finished. The break shows up between two numbers, not as a number that already has too many shaded cells on the board you are looking at. Leaving the cell empty does not start that break. The cell is empty. Hint writes that one dot and lights only that cell. It does not light a number.

On this figure the cell is row 1, column 1, the corner 1, and the grid is still blank. There is no 0. One number and the pairs find nothing, so the first press is the try. The two numbers in the failed try are the 4 at row 2, column 3 and the 2 at row 2, column 4. After the shade, the 4 still needs two shaded cells the 2 does not see, and only one of those cells is still open. The empty mark on row 1, column 1 does not by itself fill the rest of the grid. Easy and medium labels do not offer this step.

Leaving it empty fails Hard

The other direction is the same try. Leave this cell empty, and the counts cannot be finished. The break is again two numbers, not a coral count on the board in front of you. A shade here lets the earlier sentences finish the grid. The cell is shaded. Hint writes that one shade and lights only that cell.

On this figure the cell is row 1, column 4, the third press. Two dots are already on row 1 column 2 and row 1 column 3, from the same kind of try. The article follows the ladder: a shade that fails, then an empty cell that fails. On this board the first two presses are the shade that fails, and this press is the empty cell that fails. The two numbers in the failed try are the 1 at row 1, column 3 and the 2 at row 2, column 3. The 2 needs one shaded cell the 1 does not see, and in that try those cells are already empty. No 5×5 hard grid says this sentence. This one is 6×6. There is no digit on row 1, column 4.

Not every hard grid says both tries. Every hard grid in this set says at least one of the two tries or the agreement in the next section. Easy and medium never say any of the three. If Hint has nothing and the grid is not finished, Check or Undo is the next move. The toast is "No forced cell from here. A shaded cell or a dot may be in the wrong place, so try Check or Undo."

Both ways agree Hard

Sometimes both marks on the cell can be finished. The cells that come out the same either way are forced. Hint writes those cells and leaves the cell you tried blank. It lights the cells it writes. It does not light the cell you were deciding.

On this figure the cell under trial is row 1, column 2. Shading it can be finished. Leaving it empty can be finished. Both ways dot row 4 column 2 and shade row 5 column 2 and row 6 column 2. The press writes those three. Row 1, column 2 stays empty, and it is not lit. The how-to describes the try that drops a broken mark. This is the other result of the same try, and the button says it once. The two finished grids are not walked here.

5Common mistakes

Check marks a number coral when the shaded cells in its neighbourhood are already too many, or when the cells still open are too few to reach it. The coral cells are those numbers. A shade that is not itself a broken number stays violet. A dot that is not on a broken number stays an ordinary dot. A board that still has room for every number is unfinished. Check says "No mistakes so far. Keep going!" Hint on a broken board says "This board has a mistake, so there is no hint yet."

A shade in the neighbourhood of a 0 is too many. On this figure the shade is the blank at row 4, column 5. The 0 at row 3, column 5 and the 0 at row 4, column 4 both see it, so both numbers go coral. The shade stays violet. Dotting five cells of the 2 at row 2, column 1, and leaving row 3, column 2 open, leaves that 2 short. The 2 goes coral. The other four dots stay ordinary dots. The 2 itself holds one of the dots, so that dot is coral with the number.

A shade or a dot in the wrong place can still leave every number able to reach its count. Check stays quiet. Hint still offers the opening step, and it does not overwrite the wrong mark. On this grid a shade at row 1, column 1 is that kind of quiet mistake. A dot on row 1, column 2, which is a cell the solution shades, is the other. Follow the button from that dot and the later "only one way" shades row 3, column 3, which the 0 at row 4, column 4 cannot hold. The wrong dot is still there. Undo, or clear the mark, and read the 0 again. That later board is not drawn.

6What to play next

Easy grids are one number at a time. Start with a 0, then a number that fills its neighbourhood, then a number that already has its shades, then a number with only one way left. A 5×5 easy grid is the short start. Medium grids add the two-count step. The one-number sentences still come first, and a medium grid can still open on a 0. Hard grids add the one-cell try: a shade that fails, an empty cell that fails, or both ways agreeing. The daily puzzle is 8×8 medium.

1. Easy5×5The four one-number sentences, except "already enough", which this size's easy grids do not use. One of them opens on a 6 rather than a 0.Play 5×5 →
2. Easy6×6The same sentences, including "already enough".Play 6×6 →
3. Easy7×7The same sentences, on a larger neighbourhood.Play 7×7 →
4. Easy8×8The same sentences.Play 8×8 →
5. Easy9×9The same sentences. One grid at this size never says "only one way left".Play 9×9 →
6. Easy10×10The same sentences.Play 10×10 →
7. Medium5×5Overlapping neighbourhoods, after any one-number step that is ready. One of them still opens on a 0.Play 5×5 →
8. Medium6×6The same.Play 6×6 →
9. Medium7×7The same.Play 7×7 →
10. Medium8×8The daily size.Play 8×8 →Today's daily →
11. Medium9×9The same.Play 9×9 →
12. Medium10×10The same.Play 10×10 →
13. Hard5×5The try. This size says the shade that fails. It does not say the empty cell that fails.Play 5×5 →
14. Hard6×6Both try directions, and, on one grid, both ways agreeing.Play 6×6 →
15. Hard7×7The try, plus the earlier sentences.Play 7×7 →
16. Hard8×8The same.Play 8×8 →
17. Hard9×9The same.Play 9×9 →
18. Hard10×10The same.Play 10×10 →

12×12 and 15×15 are for print only, in the same three difficulties. A printed answer fills the shaded cells and leaves the dots off the page. Four 5×5, 6×6, or 7×7 grids share a sheet. Two 8×8, 9×9, or 10×10 grids share a sheet. A 12×12 or a 15×15 has the sheet to itself. The printable page is Mosaic packs.

• GuideMinesweeperA neighbourhood count whose number does not include itself. The mark is a mine.
• GuideSudokuEach digit once in every row, column and box.
• GuideHashiCount bridges, never cross, connect every island.
• GuideBinairoEvery cell is one of two marks.
• GuideKakurasuShade cells so each row and column hits its sum.
• GuideStar BattleOne or two stars in every row, column and region. They never touch.
• GuideSlitherlinkDraw one loop. Start from the 0s and the 3s.
• GuideNonogramsOverlap long clues, cross the gaps, and read the crossing line.
• GuideHitoriShade repeats, never side by side, keep white connected.
• GuideNurikabeGrow each island to its number and keep one sea.
• GuideLight UpLight every cell. Start beside the 4s and the 0s.
• GuideKakuroOne-way sums first, then short runs.
• GuideKiller SudokuCage sums, then the rest of the line.
• GuideJigsaw SudokuFollow the thick walls. Each region has its own shape.
• GuideFutoshikiLess-than and greater-than signs between neighbours.
• GuideRenzokuDots between cells. An empty gap means not one apart.
• GuideSkyscrapersEach clue counts the heights it can see.
• GuideCalcudokuOne-way cages first, then the rest of the line.
• GuideShikakuEach number is an area. Start with the ones that fit one way.
• GuideTentsPlace one tent beside every tree and match the counts.
• GuideMasyuTurn on black pearls, go straight through white ones.
• GuideThermometersFill each tube from the bulb so a plain count matches.