Suguru (Tectonic) rules
Suguru, also called Tectonic, is played on a grid divided into regions outlined in bold. A region of one cell holds a 1, a region of two cells holds 1 and 2, and so on: a region of k cells holds every number from 1 to k exactly once. The second rule is what makes it Suguru: two cells with the same number may never touch, not side by side and not corner to corner, even when they are in different regions.
That is all there is to it. There are no rows or columns to fill as in Sudoku, so a 1 can appear many times in a line, as long as no two 1s touch. The example is a real 6×6 puzzle from the game at Medium: nine numbers to start with, regions of one, three, four and five cells, and exactly one way to fill it.
- A region of k cells holds the numbers 1 to k, each once.
- Equal numbers never touch, not even diagonally.
- The same number can appear many times on the board, in cells that don't touch.
- A proper Suguru has exactly one solution, and every puzzle here does.
How to play Suguru online
Tap or click a cell, then a number. The number pad only offers the numbers that fit the cell's region, and with “Show mistakes right away” switched on, a number that doesn't belong turns red at once. Switch it off under the board if you'd rather find your own mistakes, and use Check when you want to know.
Notes are the pencil marks most players use. Press Notes (or N) and the numbers you tap go into the cell as small candidates, or hold Shift with a number to add one without switching. Auto-notes fills every empty cell with the numbers it can still take: 1 to its region's size, minus the numbers already in its region and in the eight cells around it. When you place a number, it disappears from the notes of every cell it rules out, and Undo and Redo bring notes back along with the numbers.
Hint explains the next step instead of filling in a cell. It names the technique, highlights the cells it uses and says why in a sentence, for example “D2 is the only cell in its 4-cell region where a 2 can go”. You can apply it, or close it and make the move yourself. If a number on the board is wrong, or your notes have lost the right number, the hint says that first. Hints work at every level and in every language on the site.
Boards come in 5×5, 6×6, 7×7, 8×8, 9×9, 10×10, 12×12 and 15×15. By default every region has one to five cells, as in most printed Suguru books; switch on Bigger regions under the board for regions of six and seven cells. A new puzzle takes a few seconds at most, and the next one is made while you play, so New puzzle is usually instant. On 12×12 and 15×15, Focus gives the whole screen to the board, and the size slider beside it makes the cells bigger; an enlarged board scrolls inside its frame.
| To do this | Mouse or touch | Keyboard |
|---|---|---|
| Place a number | A cell, then a number | 1–7 |
| Add or remove a note | Notes, then a number | Shift + 1–7 |
| Fill in every candidate | Auto-notes | A |
| Get a hint | Hint | H, then Enter to apply |
| Undo, redo | Undo, Redo | Ctrl + Z, Ctrl + Y |
| Pause | The button by the timer | P |
| Make the board bigger | Focus or the size dial (12×12 and up) | Esc leaves Focus |
| Move between cells | – | Arrow keys, after clicking a cell |
What Easy, Medium, Hard and Expert mean
Our levels are set by the techniques a puzzle needs, not by how many numbers it starts with. Before you see a puzzle, the same engine that gives the hints solves it step by step, and the hardest step it needed decides the level. Every Medium needs at least one step that singles can't do, every Hard a touching pair, and every Expert a “what if?”: the techniques below, in that order. The table shows what that means on an 8×8.
| Level | Clues | Steps | Needs beyond singles |
|---|---|---|---|
| Easy | 31% | 44 | Nothing |
| Medium | 23% | 53 | A cell that touches every spot (100%) |
| Hard | 17% | 72 | A touching pair (100%), a pair in a region (19%) |
| Expert | 14% | 82 | A “what if?” (100%), a touching pair (88%) |
Averages over 150 puzzles per level, 8×8 with classic regions, from the generator that runs this page, solved with the hint techniques. Clues: the share of the 64 cells filled at the start. Steps: hint steps to solve it.
Daily Suguru, sharing, printing and your stats
The Daily puzzle is an 8×8 that everyone gets on the same day, new at midnight on your clock: Easy on Mondays, Medium on Tuesdays, Wednesdays and Sundays, Hard on Thursdays and Fridays, and Expert on Saturdays. Solve it each day to grow your days in a row; the puzzle you were playing waits until you come back to it.
Share copies a link that carries the whole puzzle, so a friend gets exactly the same grid, and the puzzle number under the board shows you are on the same one. Print makes a PDF of the puzzle you are playing, with its solution, or a pack of up to 50 new puzzles at the size and level you choose, one, two or four to a page, with or without bigger regions. Every printed puzzle is checked again by a separate solution counter before it goes on the page.
Your stats count the puzzles you solve at each size and level, with your best and average times; only solves without hints set a best time. They are saved in this browser only, and so is your game: close the tab, and it is waiting when you come back.
How to solve Suguru: start with the singles
Most of every Suguru, even an Expert, falls to two simple steps. The first: a region needs every number from 1 to its size, so when a number fits only one of its cells, it goes there. In the example, the 4-cell region B3, C2, C3, D2 still needs a 2. The 2 in B2 touches B3, C2 and C3, so none of them can be 2, and the 2 goes in D2.
The second is the cell with only one number left. Take the numbers its region allows, cross off those already in the region and those in the eight cells around it, and see what remains. Small regions are the place to start, because their choice is short.
- A one-cell region is always 1.
- Every number you place rules itself out of the eight cells around it.
- Look for a region's biggest number first: fewer regions have one, so it has fewer places to go.
- Notes pay off from Medium up, and Auto-notes fills them in one go.
A cell that touches every spot
This is the first step beyond singles, and every Medium needs it. A region's number has to go in one of a few cells; if one cell outside the region touches all of them, that cell can't hold the number, wherever it ends up. In the example the 5-cell region B1, B2, B3, C1, C2 already has 1, 2 and 5, so its 3 goes in C1 or C2. D2 touches both, so D2 can't be 3.
It works for any spots that one cell touches: two or three cells side by side, or a corner of a 2×2 square. Look for it whenever a region is down to two or three candidates for a number.
Pairs inside a region
When two cells of a region can only hold the same two numbers, those numbers are theirs, and no other cell of the region can take them: a naked pair, as Sudoku players call it. In the example, D4 and E4 can only be 4 or 5, so the 4 and the 5 of the 5-cell region D4, E4, F3, F4, F5 are in those two cells. F4 loses its 4 and 5, and F5 loses its 5.
The mirror image is the hidden pair: two numbers the region still needs that fit in only two of its cells. Those cells hold those two numbers, so any other candidates in them can go. Triples work the same way, with three cells and three numbers.
Touching pairs across regions
This is the step that sets Hard apart. Two cells that touch can never hold the same number, so if both can only be the same two numbers, they hold one each, even when they belong to different regions. Every cell that touches both of them, or shares a region with both, then loses those two numbers. In the example, D2 and D3 touch and can only be 1 or 3. C3 touches both, so it loses 1 and 3 and can only be 2; E3 touches both too, and loses its 1.
The same goes for three cells that all touch one another, like three cells of a 2×2 square, with three numbers between them.
What if? The Expert step
When no simpler step is left, an Expert puzzle needs a short trial: take a cell with two candidates, suppose one of them, and follow the singles it forces. If that runs into a dead end, the supposition was wrong. In the example, F2 can be 3 or 4. Suppose it were 4: then E3 would have to be 1, D1 a 4, F4 a 3 and E2 a 2, and D2 would have no number left, because the 4 in D1 and the 2 in E2 both touch it. So F2 can't be 4: it is 3.
Our hint always picks the shortest chain it can find, and the Expert puzzles here never need more than this: one supposition followed by singles.
How we make every Suguru
Making a classic Suguru by computer is harder than it looks. When we built this generator, we first drew regions of one to five cells at random and then searched for numbers to fill them. Only 3 in 100 random 8×8 layouts could be filled at all, 1 in 100 at 10×10, and none of 1,619 at 12×12. That is one reason some Suguru sites use regions of six and seven cells on big boards.
Ours grows the layout one region at a time and keeps a complete fill of numbers alongside it: each new region is cut where the numbers already read 1 to its size, so the layout can always be filled. Then it takes out starting numbers one by one, keeping each removal only if the puzzle can still be solved with the techniques of its level, which also proves it has exactly one solution. Easy, Medium and Hard keep a few extra numbers so they never look bare, but only where the level stays the same.
Suguru vs Sudoku and other number puzzles
Like Sudoku, Suguru is about placing numbers that may not repeat, but its regions vary in shape and size and there are no rows or columns: the touching rule does their job. Jigsaw Sudoku keeps irregular regions and adds Sudoku's rows and columns; Ripple Effect fills regions with 1 up to their size too, but keeps equal numbers apart by a distance that grows with the number; in Fillomino you draw the regions yourself from the numbers. If you like the arithmetic side, Kakuro and Str8ts are the next step.
Suguru was created by the Japanese puzzle designer Naoki Inaba, one of the most prolific inventors of logic puzzles, under the name Number Blocks. It spread through European puzzle magazines as Tectonic, the name players in the Netherlands, Belgium and Germany still use, while Suguru is the name most used elsewhere.