Play Shape Sudoku Online

What is Shape Sudoku?

Shape Sudoku is sudoku played with nine shapes instead of nine digits. Fill the 9×9 grid so that:

• every row holds each of the nine shapes once;
• every column does too;
• and so does every 3×3 box.

The shapes are the circle ●, square ■, triangle ▲, diamond ◆, star ★, hexagon ⬡, cross ✚, heart ♥ and arrow ▼, in the order of the legend above the grid and the buttons below it. Sudoku never adds or compares numbers, so nothing is lost in the swap: every technique that works on a classic board works here shape for shape, and Letter Sudoku, Color Sudoku, Symbol and Emoji Sudoku are the same puzzle drawn in other pictures.

How do you find where a shape goes?

One shape at a time. Pick a shape, find every copy of it already on the board, and look at a box that still needs it: each copy rules out its own row and column. When only one empty square of the box is left, the shape goes there, whatever else that square could hold on its own. That is a hidden single:

The colours make that sweep quick: select a square holding the shape and every copy of it on the board lights up. The same sweep works along a row or a column: a shape with one place left in a line goes there. And a square whose row, column and box already hold eight different shapes takes the ninth. Between them, those two moves finish every Easy and Medium board on this page.

What do Hard boards add?

Locked candidates. When singles run out, put the shapes each empty square can still hold in its pencil marks — the Notes button draws them small, each in its own colour — and look inside one box at a time. If a shape’s places in the box all lie in one row or column, the box’s copy of that shape is that line’s copy too, so it comes out of the rest of the line:

It works the other way round as well: a shape confined to one box within a row or column comes out of the rest of that box. Hard boards are dug so that singles and locked candidates finish them.

And Expert boards?

Naked pairs. Two squares of one row, column or box that can each hold only the same two shapes will take those two between them, whichever way round, so no other square of that row, column or box can have either:

Expert boards are dug so that singles, locked candidates and naked pairs finish them, and they start with the fewest shapes.

Were the boards on this page fair?

Not for their first six days. From 7 April 2026 the generator took shapes out without checking anything, and 140 of 160 boards we dealt from that first version have more than one answer. From 13 April it checked every shape it took out with a full search, and we re-counted 160 of its boards with a separate counter to confirm it: each had exactly one answer. What it never checked was how a board would be solved, though the page said every solution “can always be reached through logical deduction — no guessing required”.

Each level only had a number of shapes to leave, so the names meant less than they said. Expert promised “Only about 22 givens” and left 22 on 4 boards in 40, leaving a median of 25, much the same as Hard’s 26. The page said Hard “Demands intermediate techniques like naked pairs, pointing pairs, and box/line reduction” and Expert “Requires advanced strategies such as X-Wing, Swordfish, and XY-Wing”, yet singles alone finished 22 of 40 old Hard boards and 15 of 40 old Expert ones. And a solver that knows singles, locked candidates, pairs, triples and the X-Wing could not finish 26 of the 160 boards — 3 Medium, 12 Hard and 11 Expert.

The generator was rewritten in October 2026, the same fix as Letter, Color, Symbol and Emoji Sudoku’s, which dealt from the same code. It now takes a shape out only while the level’s own steps still solve the board, which also proves the board has exactly one answer. Two faults in how the board was drawn went at the same time. On the dark theme the violet hexagon and the indigo arrow were hard to see, at 2.8:1 and 2.6:1 against the squares, and every pencil mark turned the same grey; each shape now has a lighter shade of its own colour there. And a wrong shape was marked only by turning red, which cannot mark a wrong diamond, red already; a wrong or clashing shape now also gets a red dot in its corner.

How do the four levels differ?

By how many shapes are given, and by the steps a board is dug for. We dealt 40 fresh boards per level from the new generator, and 40 per level from the old one:

40 boards per level, fixed seed. Expert digs toward 22 shapes as far as its steps allow and keeps the fewest of up to six tries: 22 to 25, median 23. On the new boards nothing past naked pairs was ever needed: 3 Hard boards could not be finished without locked candidates, and of the Expert boards, 6 needed locked candidates and 3 naked pairs.

At the top the new levels are easier than the old ones, and fair all the way down. Most Hard and Expert boards now fall to singles alone, and what makes them harder is having fewer shapes to start from — 26, and about 23 — against Medium’s 32. The old Hard and Expert were harder mainly because more than a quarter of their boards needed more than any level here teaches.

Which level should you play?

Start on Easy if sudoku is new to you, or on Medium if you know it with numbers. Easy gives 40 shapes and Medium 32, and both fall to singles alone. The page opens on Medium.

Scan by colour for the long sweeps across the board and by outline when you check one square. Notes pay off more here than on a number board: fill them in early, and a shape’s candidates show across the grid in its own colour without reading each square. Hard and Expert then add the two moves above, on boards with fewer shapes to start from.

What do the buttons do?

Select a square, then a shape; the page opens on Medium. Selecting a square highlights its row, its column and its box, and every copy of the shape in it. A wrong shape turns red and gets a red dot in its corner the moment it goes in, and so does one that repeats a shape already in its row, column or box. Under the grid:

• Notes turns pencil marks on and off; they show as small shapes in their own colours. A correct shape clears itself from the notes of its row, its column and its box; a wrong one leaves the other squares’ notes alone.
• Erase clears the selected square, and pressing the same shape twice does the same.
• Undo takes back the last change to a square, though not the notes a correct shape cleared elsewhere, and not the Mistakes count.
• Hint fills one square with its answer, picked at random rather than the square you could work out next.
• Solve asks first, then fills the grid and stops the timer.
• New Game deals another board at the level you are on; the level buttons deal one at theirs.

From a keyboard: 1–9 for the shapes in button order (1 circle through 9 arrow), the arrow keys, Backspace or Delete and Ctrl+Z; shortcuts such as Ctrl+1 are left to the browser. The board is saved in this browser after every move, so it is waiting when you come back.

Where to go next

The same puzzle in other pictures: Symbol Sudoku has card suits, a note and a few shapes, each in its own colour, and Emoji Sudoku nine emoji.