Shakashaka Logic Puzzle
Shade triangles to make rectangles. Shade a right triangle in a white cell, or mark the cell with a dot, so every white region that closes is a rectangle and each number matches its neighbours.
Drag to a corner, or tap it. Right-click or hold for a dot.
How to play Shakashaka
Place a triangle
Choose Triangle. Drag from the cell toward a corner, or tap that side of the cell. The black right angle sits in the corner you chose. Tap the same corner again to clear it.
Mark a cell white
Switch to Dot, or press period or Space, to put a small dot in the cell. Right-click or a long press places a dot from either mode. A dot replaces a triangle, and a triangle replaces a dot.
Close the rectangles
Keep going until the triangles match. A dot and a blank cell both count as white. The puzzle is finished when every white region is a rectangle and nothing on the board clashes.
Shakashaka is a shading puzzle, also called Proof of Quilt. You place a right triangle in a white cell, or mark the cell with a dot, so the white regions form rectangles. You can play 5×5 through 10×10, plus a 6×8 rectangle, each in easy, medium, and hard. Every puzzle here has exactly one solution.
Rules
The board is a grid. Black cells are given. A black cell with a white digit from 0 to 4 is a number. A plain black cell is a wall and does not give a count. Every other cell starts white.
In a white cell you may place one right triangle. 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 is the open edge, and that edge must 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 more neighbouring triangles are already placed than the digit allows, or when too few neighbours are still free to meet the digit. Neighbours share a side. Cells that only touch a corner do not count.
The puzzle is solved when the triangles match the unique solution and no clash remains. Dots and blank cells both count as white.
Controls
Triangle and Dot sit under the board. In Triangle mode, drag from a cell toward a corner to set that orientation, or tap the corner’s side of the cell. The exact centre of a cell counts as southeast. Tap the same orientation again to clear it. In Dot mode, a tap toggles the dot.
Right-click toggles a dot in either mode. Press and hold to place a dot. A drag that leaves the cell cancels the hold. M switches between Triangle and Dot.
The arrow keys move a cell cursor. The cursor starts on the first white cell and skips black cells. 1 or Q sets northwest. 2 or E sets northeast. 3 or Z sets southwest. 4 or C sets southeast. These keys set the orientation. They do not clear a triangle that is already there. Period or Space sets a dot. Backspace, Delete, or 0 clears the cell.
Press Hint for one cell the rules already force, with a sentence saying why. The hint highlights that cell and the clue or edge that forces it, then places the mark. Press Check when you want the board checked against the rules. Undo and Redo step through your moves, and Reset clears every mark. When the triangles match, the board turns teal.
A coral cell is a clash that is already visible: a number that is already over or already unreachable, or a closed white region that is not a rectangle.
Techniques
Easy:
- clue-zero: This number is 0, so every neighbouring cell stays white.
- clue-sat: The remaining neighbours have to be triangles to meet this number.
- clue-full: This number is already met, so this cell stays white.
- blocked-side: This triangle would open onto a black cell or the border.
- blocked-empty: Every triangle here opens onto a wall, so the cell stays white.
- pair-close: The white side of this triangle must meet a matching edge.
- corner-close: Three corners of this sealed 2×2 are set, so the last cell is the fourth corner.
Medium:
- diag-straight: The side next to this triangle is white, so the same triangle continues.
- diag-white: Two matching triangles in a row leave the inner cell white.
Hard:
- diamond-propagate: This side of the rotated rectangle is already two triangles long, so it continues.
- one-level trial (probe): Every other mark in this cell leads to a contradiction.
- agree: This mark is absent from every case that is still open.
Beginner tips
Start with a 0. Every cell beside it stays white, so a dot is safe there. Then look for a number that is already full, or a number whose remaining neighbours must all be triangles.
When a triangle would open onto a black cell or the outer frame, that corner is impossible. If every corner is blocked, the cell stays white.
If you are new to Shakashaka, start with a 5×5 easy grid, or the daily 7×7 easy grid, and move up once the rectangles feel natural. Play runs from Easy → Hard on every size from 5×5 to 10×10 and on 6×8.