Rules
Shakashaka is a shading puzzle. The board is a grid of white cells and black cells. A thick frame runs around the outside. Thin lines show the cells. A black cell with a white digit from 0 to 4 is a number. The digit is how many neighbouring cells hold a triangle. Neighbours share a side. A corner touch does not count. A plain black cell is a wall and has no number. Every other cell starts white. In a white cell you place one right triangle, or a small dot. The black right angle sits in a corner, and the triangle covers half the cell. Northwest opens toward the east and the south. Northeast opens toward the west and the south. Southwest opens toward the north and the east. Southeast opens toward the north and the west. A dot means the cell stays white. A cell you have not marked is also white. A dot and a triangle cannot share a cell. Placing one replaces the other. There is no cycle through the four corners and the dot. White cells that touch along a side belong to one region. A triangle's white side has to meet white space or the matching side of another triangle. A region that is already closed is checked at once. A closed region that is not a rectangle is a clash. A region that is still open stays quiet. A number is a clash when too many neighbouring triangles are already placed, or when too few neighbours are still free to meet it. The puzzle is finished when the triangles match and every white region is a rectangle. Play and print are 5×5, 6×6, 7×7, 8×8, 9×9, 10×10, and 6×8, each at easy, medium, and hard. The 6×8 board is 6 rows by 8 columns. The daily puzzle is a 7×7 easy grid. People also look this up as Proof of Quilt.
- A number. A white digit from 0 to 4 is how many neighbouring cells hold a triangle. Neighbours share a side. A corner touch does not count. A plain black cell is a wall and has no number.
- A triangle. The black right angle sits in one corner, and the triangle covers half the cell. Northwest opens east and south. Northeast opens west and south. Southwest opens north and east. Southeast opens north and west.
- A dot. A dot means the cell stays white. A cell you have not marked is also white. A dot and a triangle cannot share a cell. Placing one replaces the other.
- A clash. A closed white region that is not a rectangle is a clash. So is a number that already has too many neighbouring triangles, or too few neighbours still free to meet it.
The picture of a finished grid draws the solved triangles in teal. It does not draw a dot, and it does not draw a yellow line. The frame is teal. White cells are a soft teal. Black cells stay ink. Digits stay white. A printed puzzle page shows the black cells and the white digits, with no triangles. A printed answer fills each triangle black and leaves white cells white. On screen, the solved picture uses teal instead of black. The PDF is black and white.
- Number
- Triangle
- Dot
- Clash
Choose Triangle or Dot under the board. Triangle starts selected. Drag toward a corner, or tap that side of the cell. The exact centre counts as southeast. Tap the same corner again to clear it. In Dot mode, a tap places a dot, and a tap on a dot clears it. Right-click places or clears a dot from either mode. Press and hold to place a dot. One press is one cell. Arrow keys move from cell to cell, skip black cells, and stop at the edge. The cursor starts on the first white cell. 1 or Q sets northwest. 2 or E sets northeast. 3 or Z sets southwest. 4 or C sets southeast. Those keys set the corner. They do not clear a triangle that is already there. Period or Space sets a dot. Backspace,Delete, or 0 clears the cell. M switches Triangle and Dot.
Press Hint for one cell the black cells already force, with a sentence saying why. Hint lights that cell, and the number or the white side it used, then places the mark. One press places one triangle or one dot, and undo takes that press back in one step. Press Check when you want the board checked. A legal unfinished board gets "No mistakes so far. Keep going!" That is also the sentence while a clash is painted and a blank cell remains. A fully marked board that still breaks a rule gets "Something breaks the rules. Look for the marked cells." Hint on that finished broken board gets "This board has a mistake, so there is no hint yet." If Hint finds nothing on a legal board, it says "No forced cell from here. Try Check or Undo if a triangle looks wrong." Undo and Redo step through the marks. Reset clears every mark. When the triangles match, they turn teal, the white cells turn a soft teal, the black cells stay ink, and the frame turns teal. Any dot on the board is hidden. The dialog title is "Solved!" The dialog body is "The triangles match, and every white region is a rectangle." The line under the board is "Drag to a corner, or tap it. Right-click or hold for a dot." Once the grid is solved, that line is "White regions are rectangles." The Mistakes counter counts how many times Check found a fully marked board that still broke a rule. It is not a score.
A coral cell is a clash that is already on the board. With error highlighting off, none of that coral is drawn. A number that is already over, or already unreachable, turns that black cell coral and leaves the digit white. The triangles beside it stay ink. A closed white region that is not a rectangle turns those cells a soft coral, and a triangle there turns coral. Print pages cannot show the yellow, the coral, the violet dots, or the teal.
Numbers
A white digit is how many cells that share a side hold a triangle. A corner touch does not count. A 0 keeps every neighbouring cell white, so the button writes a dot. A number whose free neighbours are exactly the ones it still needs writes a triangle in the next of those cells. A number that already has its triangles writes a dot in a neighbour that is still free. One press writes one cell. The numbered cell is washed with it, and it stays black. There is no yellow line. A blank grid in this set does not open on a number. The first press is the cell that stays white, in the walls section. An easy grid returns all three of these sentences.
This number is 0 Easy
A 0 means no neighbour holds a triangle. On this grid the 0 in row 2 column 5 has one white neighbour, row 2 column 4. The cells above it and below it are black, and the frame is to its right. The press writes a dot in row 2 column 4. The 0 is washed with it and stays black. There is no yellow line. The dot is violet on a soft yellow cell.
The grid is still unfinished. This is not an opening. The button on a blank grid writes the cell that stays white first. Several of those dots are already on this picture, and so are two triangles the numbers forced earlier. They stay ink, or violet on paper. This press does not move them. The toast is "This number is 0, so every neighbouring cell stays white." Easy, medium, and hard all place this dot. It does not finish the grid. The last press on this grid is the same triangle continuing, and that press solves it. Hint skips the toast on a finishing press.
Soft yellow on row 2 column 4. The 0 in row 2 column 5 stays black, and the digit stays white. The new dot is violet. No yellow line. The grid is not finished.
The remaining neighbours Easy
Some numbers still need triangles, and the free neighbours are exactly the ones that have to hold them. On this grid the 1 in row 3 column 4 has one white neighbour left, row 4 column 4. The cell to its west is already a dot. The other two sides are black. The press writes a northwest triangle in row 4 column 4. That is the corner that can sit there: the other three would open onto a black cell. The sentence the button shows is the number sentence. The new triangle is ink. The white half of row 4 column 4 is soft yellow. The 1 stays black. There is no yellow line.
The grid is still unfinished. This is not an opening. The six dots already on the board are the cells that stay white, from the opening presses. They stay violet on paper. The toast is "The remaining neighbours have to be triangles to meet this number." Easy, medium, and hard all place this triangle. It does not finish the grid. The same grid says this sentence twice more, and a later corner solves it. That corner is not drawn here.
Northwest in row 4 column 4. The triangle is ink, and its white half is soft yellow. The 1 in row 3 column 4 stays black. No yellow line. The grid is not finished.
The number is already met Easy
Once the triangles beside a number add up to the digit, every other neighbour stays white. On this grid the 1 in row 4 column 6 already has its triangle, a northeast triangle in row 5 column 6. The cell above the 1, row 3 column 6, is still empty. The press writes a dot there. The 1 is washed with it and stays black. There is no yellow line.
The grid is still unfinished. This is not an opening. The dots and triangles already on the board stay as they are. This wide grid is 6 rows by 8 columns. The toast is "This number is already met, so this cell stays white." Easy, medium, and hard all place this dot. It does not finish the grid. One catalog grid still has this sentence after the triangles already match. The live button never shows that press.
Soft yellow on row 3 column 6. The 1 in row 4 column 6 stays black. The northeast triangle in row 5 column 6 stays ink. No yellow line. The grid is not finished.
Walls
A triangle that would open onto a black cell or the outer frame cannot sit in that corner. The button can name that one corner. On these grids it never does. The sentence would be "This triangle would open onto a black cell or the border." When every corner is blocked, the cell stays white, and the button writes a dot. The yellow line is the first side that is a wall, in the order top, right, bottom, left. It is not the only wall. A blank grid in this set opens on that dot. The same sentence then writes the other forced white cells, one cell at a time.
Every corner is blocked Easy
Some cells cannot hold any triangle, because each corner would open onto a black cell or the frame. On this blank grid the press writes a dot in row 1 column 1. The top of the cell is the frame. The right side is the 0 in row 1 column 2. The bottom is the 0 in row 2 column 1. The left side is the frame. The yellow line is the top edge. It is the first blocked side. It is not the only wall. The cell is soft yellow, and the dot is violet.
The grid is still unfinished. This is the opening press on every grid in this set. The same sentence writes five more dots on this grid, one cell at a time. A corner that is blocked while another corner still fits is a different sentence. The button never writes that sentence on these grids. The toast is "Every triangle here opens onto a wall, so the cell stays white." Easy, medium, and hard all place this dot. It does not finish the grid.
Soft yellow on row 1 column 1. A violet dot. A yellow line on the top edge. First press. The grid is not finished.
Rectangles
The white side of a triangle has to meet white space or the matching white side of another triangle. The button writes that neighbour. Sometimes the neighbour is the matching triangle. Sometimes it stays white, and the mark is a dot. The yellow line is the white side of the triangle that is already there, so both cells wash. Three corners of a sealed 2×2 force the last corner. The two outward sides of that cell are already closed by the frame, a black cell, or the black leg of a triangle. A 2×2 that still has a way out is not this sentence. Both sentences are available on an easy grid. A blank grid in this set does not open on either one.
A matching edge Easy
The white side of a triangle has to meet a matching edge. On this grid row 1 column 2 is already a northwest triangle. Its south side faces row 2 column 2. The press writes a southwest triangle there, so the two white sides meet. The yellow line is the bottom edge of row 1 column 2, the side the sentence is about. Both cells wash. Both triangles are ink. The white half of each washed cell is soft yellow.
The same sentence also writes a dot, when the neighbour has to stay white. On this grid row 2 column 4 is a northeast triangle. Its west side faces row 2 column 3. The press writes a dot in row 2 column 3. The yellow line is the left edge of row 2 column 4. Both cells wash. The dot is violet. The triangle stays ink. On these grids a dot is the more common of the two marks. The sentence is the same.
Both presses leave the grid unfinished. Neither is an opening. The dots and triangles from earlier presses stay ink or violet on paper, except the two cells this press washes. The toast, both times, is "The white side of this triangle must meet a matching edge." Easy, medium, and hard return each hint. Neither press finishes. A later press on this grid does.
Southwest in row 2 column 2 meets the south side of the northwest triangle in row 1 column 2. A yellow line on the bottom of row 1 column 2. Both cells washed. Both triangles ink. The grid is not finished.
A dot in row 2 column 3, on the west side of the northeast triangle in row 2 column 4. A yellow line on the left of that triangle. Both cells washed. The dot is violet. The triangle stays ink. The grid is not finished.
The last corner Easy
Three corners of a 2×2 can force the fourth, once the last cell has no way out. On this grid row 1 column 2 is northwest, row 1 column 3 is northeast, and row 2 column 3 is southeast. Row 2 column 2 is the last cell. Its west side is the black cell in row 2 column 1. Its south side meets the northeast triangle in row 3 column 2, and that triangle's black edge faces north, so the side is closed. The press writes a southwest triangle in row 2 column 2. The yellow line is the bottom edge of row 2 column 2. The new triangle is ink. The white half of the cell is soft yellow. The three triangles already there stay ink.
The grid is still unfinished. This is not an opening. The same grid writes two more corners after this one. The second of those solves the grid. Both last corners on a 5×5 in this set are the press that solves, so they are not the picture. The toast is "Three corners of this sealed 2×2 are set, so the last cell is the fourth corner." Easy, medium, and hard all place this triangle. It does not finish the grid.
Southwest in row 2 column 2. A yellow line on the bottom of that cell. The new triangle is ink. The three triangles already in the 2×2 stay ink. The grid is not finished.
Straight on
When the white side next to a triangle is already white, the same triangle continues one step. The yellow line is that white side. The new triangle is ink. Two matching triangles in a row can also force the inner cell to stay white. The sentence would be "Two matching triangles in a row leave the inner cell white." The button never writes that sentence on these grids. A blank easy grid never says the continuation. On an easy grid, Hint has nothing to place when this is the next step. Medium and hard return it.
The same triangle continues Medium
When the side next to a triangle is already white, the same triangle continues. On this grid row 2 column 2 is a southwest triangle, and the cell to its east, row 2 column 3, is a dot. The press writes the same southwest triangle in row 3 column 3, one step down and to the right. The yellow line is the right edge of row 2 column 2. Both cells wash. Both triangles are ink. The run is still a single triangle, so this is not yet the long side.
The grid is still unfinished. This is not an opening. The next press on this grid is another continuation, and it solves. Hint skips the toast on that finishing press. On an easy grid, Hint has nothing to place here. The toast is "No forced cell from here. Try Check or Undo if a triangle looks wrong." Medium and hard place the triangle. The sentence they show is "The side next to this triangle is white, so the same triangle continues."
The east side of the southwest triangle in row 2 column 2 is a dot, so the same triangle continues into row 3 column 3. A yellow line on the right of row 2 column 2. Both cells washed. Both triangles ink. The grid is not finished.
The long side
A diagonal run that is already two triangles long is the same idea one step further, and the button uses a different sentence. The picture leaves the grid unfinished. The button can also try every other mark in one cell. The sentence would be "Every other mark in this cell leads to a contradiction." On these grids that trial never writes. What does write, on two hard grids, is a dot that every still-open case keeps. There is no number and no yellow line. A blank easy grid, and a blank medium grid, never say either sentence. Easy and medium have nothing to place when one of them is the next step. A hard grid still opens on the cell that stays white.
The side continues Hard
The same continuation has its own sentence once the diagonal is already two triangles long. On this grid row 3 column 5 and row 4 column 4 are both northwest triangles. The cell south of row 4 column 4 is a dot, so that side is white. The press writes another northwest triangle in row 5 column 3. The yellow line is the bottom edge of row 4 column 4. Both cells wash. The new triangle is ink. The two triangles already in the run stay ink.
The grid is still unfinished. This is not an opening. This grid opened on the cell that stays white. The next presses are another continuation and then a long side that solves. The one that solves is not drawn. Easy and medium have nothing to place here. The toast is "This side of the rotated rectangle is already two triangles long, so it continues." Hard places the triangle. It does not finish the grid. Every long side on a 5×5 hard grid in this set is the press that solves. Those are not the picture. The one-cell trial, which would keep a mark because every other mark breaks a rule, never writes on these grids.
The northwest run of row 3 column 5 and row 4 column 4 continues into row 5 column 3. A yellow line on the bottom of row 4 column 4, beside the dot in row 5 column 4. Both washed cells. The new triangle is ink. The grid is not finished.
This mark is absent Hard
More than one mark can still look possible in a cell. The button follows the cases that are still open. When one mark is missing from all of them, that mark is out, and what remains is written. On this grid the press writes a dot in row 4 column 4. There is no number. There is no yellow line. The cell is soft yellow, and the dot is violet. The triangles already around it stay ink.
The grid is still unfinished. This is not an opening. The next press is a continuation, and it does not solve the grid. Easy and medium have nothing to place here. The picture does not show the cases. The toast is "This mark is absent from every case that is still open." Hard places the dot. It does not finish the grid. The other grid that says this sentence is also 6×6 hard, and that press is a dot as well.
Soft yellow on row 4 column 4. A violet dot. No number washed with it. No yellow line. The triangles already around the cell stay ink. The grid is not finished.
Common mistakes
A clash can show up while blank cells remain. The black cell of a number that is already over, or already unreachable, turns coral. A closed white region that is not a rectangle turns those cells a soft coral. Check, while a blank cell remains, still says "No mistakes so far. Keep going!" Hint still has a next cell on that board. The pictures of the number stop before that press, so the coral is what you see. When every white cell is marked and the board is still broken, Check says "Something breaks the rules. Look for the marked cells." Hint then says "This board has a mistake, so there is no hint yet." That picture draws no yellow. A wrong triangle can also sit there with no coral at all, while the region is still open. Then Check says to keep going, and Hint offers the next cell. The wrong triangle stays, and the new dot is the one on the soft yellow cell. With error highlighting off, the same clashes paint nothing coral.
Four pictures, all on the same 5×5.
A southeast triangle in row 1 column 4. The 0 in row 2 column 4 has no other white neighbour. The black cell is coral. The digit stays white. The triangle stays ink. Blank cells remain, so Check says "No mistakes so far. Keep going!" Hint would still offer the opening dot. This picture does not draw that yellow line. The wrong triangle is not on that cell, so the press would leave it.
A dot in row 4 column 5. The 1 in row 3 column 5 has no other white neighbour. The black cell is coral. The digit stays white. The dot stays violet. Check says "No mistakes so far. Keep going!" Hint would still offer the opening dot. This picture does not draw it.
The finished marks, with a northwest triangle in row 1 column 5 instead of a dot. That triangle opens east onto the frame and south onto the black cell in row 2 column 5. The white region is closed, and it is not a rectangle. Soft coral on that cell. The triangle is coral. The other triangles stay ink. The other dots stay violet, because the board is not solved. Check says "Something breaks the rules. Look for the marked cells." Hint says "This board has a mistake, so there is no hint yet." No yellow line.
A northeast triangle in row 1 column 5. The solution there is white. The region is still open, because the cells beside it are blank. Before the hint the board is legal and unfinished. Nothing is coral. Check says "No mistakes so far. Keep going!" The picture is after the opening hint. The wrong triangle stays ink. Row 1 column 1 is a violet dot on a soft yellow cell, with a yellow line on its top edge. No coral.
What to play next
Every grid opens on a cell that stays white, because every triangle there would open onto a wall. Easy grids then use the numbers, a matching edge, and sometimes the last corner. They do not say the continuation, the long side, or a mark that is absent from every open case. Start on a 5×5 easy grid, or on the daily 7×7 easy grid. Medium grids add the continuation. A medium grid still opens on the cell that stays white, and it finishes on that continuation. Hard grids add the long side, or, on two 6×6 grids, a mark that is absent from every open case. A hard grid still opens on the cell that stays white. The single blocked corner, the white cell between two matching triangles, and the one-cell trial do not come up as their own hint. An easy grid does not return the continuation, the long side, or the absent mark. A medium grid does not return the long side or the absent mark.
A printed puzzle page shows the black cells and the white digits. A printed answer fills each triangle and leaves white cells white. Dots are not printed. Four 5×5, 6×6, or 7×7 grids share a sheet. Two 8×8, 9×9, 10×10, or 6×8 grids share a sheet. Large print is one grid on the sheet. A single pack is 8 puzzles. The starter pack is 21, one of every size and difficulty. The printable page isShakashaka packs.
- Easy5×5The cell that stays white, then the remaining neighbours. Two grids finish on the last corner. One finishes on a matching edge. They do not say a 0, a number that is already met, or any later sentence. All three open on the cell that stays white. The rules picture, the walls picture, the remaining-neighbours picture, and the mistake pictures are one of these grids.Play 5×5 →
- Easy6×6The cell that stays white, the remaining neighbours, and a matching edge. One grid also says a 0. All three finish on the last corner. They do not say a later sentence. The last-corner picture is one of these grids.Play 6×6 →
- Easy7×7The cell that stays white and the remaining neighbours. One grid also says a matching edge. One finishes on the remaining neighbours. Two finish on the last corner. This is the daily size. They do not say a later sentence.Play 7×7 →Today's daily →
- Easy8×8The cell that stays white and the remaining neighbours. One grid also says a matching edge, and that grid finishes on it. The other two finish on the remaining neighbours. They do not say a later sentence.Play 8×8 →
- Easy9×9The cell that stays white and the remaining neighbours. One grid also says a 0. Two finish on a matching edge. One finishes on the remaining neighbours. They do not say a later sentence.Play 9×9 →
- Easy10×10The cell that stays white, then the remaining neighbours. This is the only dense size. All three finish on the remaining neighbours. They do not say a later sentence.Play 10×10 →
- Easy6×8The cell that stays white and the remaining neighbours, on the wide grid. Two grids also say a 0. One says a number that is already met, and that is the picture for that sentence. Two finish on a matching edge. One finishes on the last corner. They do not say a later sentence.Play 6×8 →
- Medium5×5The cell that stays white, the remaining neighbours, and a matching edge, then the same triangle continues. One grid also says a 0, and that is the picture for the 0. All three finish on that continuation. They do not say the long side or a mark that is absent from every open case. The matching-edge pictures and the continuation picture are one of these grids.Play 5×5 →
- Medium6×6Those sentences. Two grids also say a 0. All three finish on the same triangle continuing. They do not say the later hard sentences.Play 6×6 →
- Medium7×7Those sentences. Two grids also say a 0. All three finish on the same triangle continuing. They do not say the later hard sentences.Play 7×7 →
- Medium8×8Those sentences. One grid also says a 0. All three finish on the same triangle continuing. They do not say the later hard sentences.Play 8×8 →
- Medium9×9Those sentences. All three finish on the same triangle continuing. They do not say a 0, or the later hard sentences.Play 9×9 →
- Medium10×10Those sentences, on the dense grid. One grid also says a number that is already met. All three finish on the same triangle continuing. They do not say the later hard sentences.Play 10×10 →
- Medium6×8Those sentences, on the wide grid. One grid also says a 0. All three finish on the same triangle continuing. They do not say the later hard sentences.Play 6×8 →
- Hard5×5The cell that stays white, the remaining neighbours, and a matching edge, then the long side. One grid also says a 0. All three finish on the long side. They do not say the continuation or a mark that is absent from every open case.Play 5×5 →
- Hard6×6The cell that stays white, the remaining neighbours, and a matching edge. Two grids also say a 0. Two say a mark that is absent from every open case, and neither of those presses finishes. The picture for that sentence is one of them. One grid finishes on a matching edge, one on the same triangle continuing, and one on the long side.Play 6×6 →
- Hard7×7The cell that stays white, the remaining neighbours, and a matching edge, then the long side. One grid also says a number that is already met, and one says the same triangle continues before the long side. All three finish on the long side. The long-side picture is the press on that grid that does not finish.Play 7×7 →
- Hard8×8The cell that stays white, the remaining neighbours, a matching edge, and the long side. Two finish on the long side. One says the same triangle continues after a long side that does not finish, and that grid finishes on the continuation. They do not say a mark that is absent from every open case.Play 8×8 →
- Hard9×9The cell that stays white, the remaining neighbours, a matching edge, and the long side. One grid also says the same triangle continues between two long sides. All three finish on the long side. They do not say a mark that is absent from every open case.Play 9×9 →
- Hard10×10Those sentences, on the dense grid. All three finish on the long side. They do not say the continuation or a mark that is absent from every open case.Play 10×10 →
- Hard6×8The cell that stays white, the remaining neighbours, a number that is already met, a matching edge, and the long side, on the wide grid. One grid also says the same triangle continues between two long sides. All three finish on the long side. They do not say a mark that is absent from every open case.Play 6×8 →
There is no guide-sized seed to open. The boards above are teaching boards.