Sudoku guide
How to play Sudoku
Sudoku is a logic puzzle on a 9×9 grid. Fill every row, every column and every 3×3 box with the numbers 1 to 9, each exactly once. No maths, no guessing: just looking closely.
Sudoku rules
The rules in one minute
A Sudoku has 81 cells in nine rows, nine columns and nine 3×3 boxes. Some numbers are given, you fill in the rest. One rule covers it all:
- Every row holds 1 to 9 exactly once.
- Every column holds 1 to 9 exactly once.
- Every 3×3 box holds 1 to 9 exactly once.
The numbers could just as well be nine different symbols: you never add anything up. Every puzzle in Beasties has exactly one solution, and you can always reach it by logic alone.
How to play
Sudoku in Beasties, step by step
Board in the middle, tools and number pad right below it, and your monster peeking over the top edge, watching every move.
- Pick a cell. Its row, column and box light up, so you see at a glance which numbers are already taken.
- Tap a number. The small count under each key shows how many of that number are still missing.
- Take notes. With Notes on, numbers go into the cell as small candidates, perfect for harder levels.
- Undo and erase. Undo takes back your last step, Erase empties a cell.
- Hint, if you must. A hint fills in one correct number for 30 stars. After a hint the round gives two stars at most.
Stars and mistakes
Three stars at stake in every level
You start every level with three stars. They are what you win, so every mistake hurts a little.
- A mistake costs a star. A wrong number turns red right away and one of your three stars falls.
- Three mistakes: try again. With all three stars gone the level is lost. You start the same puzzle again.
- Solve it, keep them. The stars you have left fly into your counter. Spend them on monster parts, hints and level packs.
Difficulty levels
Four difficulties, fixed levels
The boards below are level 1 of each difficulty. Each step down gives you fewer numbers and asks for a harder technique, from plain singles in Chill to X-Wing in Devilish. None of them ever needs a guess, and within one difficulty level 1 and level 999 ask for the same.
Chill
40 numbers given
38 to 40 numbers given. Single candidates and hidden singles are enough.
Normal
32 numbers given
30 to 32 numbers given. You need hidden singles: look where a number can still go.
Tricky
27 numbers given
26 to 28 numbers given. Notes, pointing pairs, pairs and triples.
Devilish
26 numbers given
24 to 26 numbers given. X-Wing, XY-Wing and co., but never guesswork.
Chill, Normal and Tricky have 150 free levels each. You unlock the rest for free with the stars you win, or all at once with Pro. Every player gets the same puzzles in the same order, so the solutions on this site match your app, from level 1 to 999 on every difficulty. A daily puzzle comes on top: easy early in the week, tougher on the weekend. Each one you solve also moves you a level along the free season pass.
Sudoku techniques
From the first number to the last
Beasties rates every level by the hardest technique it needs. Here they are from easy to hard, each with the difficulty that first asks for it. Every example comes from a real level of the app.
Technique 1 · Chill
Naked single
A cell where eight different numbers already appear in its row, column and box. Only one number is left for it. Enough for most Chill levels.
- Pick an empty cell. Look at its row, its column and its box together.
- Cross out what you see. Every number in those three groups is taken.
- One left: write it in. Only the 9 fits.
Technique 2 · Normal
Hidden single
Take one number and one box. If that number fits in only one cell of the box, it goes there, even when the cell could hold other numbers too. The key to Normal.
- Pick a number: 7. Find every place where it already sits.
- Follow its lines. Its row and column are blocked for that number, also inside the box you look at.
- One spot left. The box still needs a 7, and only one cell can take it.
Technique 3 · Tricky
Pointing pair
Inside a box, a number can only go into cells of one row or column. Then the rest of that line cannot hold it. This is where Tricky starts.
- Notes for one number. In this box the 5 can only go into one column.
- It points along the line. Whichever of the two cells it is, that column gets its number here.
- Cross it out elsewhere. Remove that note from the rest of the column.
Technique 4 · Tricky
Naked pair
Two cells of the same row, column or box share exactly the same two candidates. Those two numbers are taken by the pair and leave every other cell of the group. Three cells with three numbers work the same way: a triple.
- Write your notes. Fill in every candidate of one box.
- Spot the pair. Two cells can only be 5 or 6.
- Clear the rest. Those two numbers belong to the pair, so they leave every other cell of the box.
Technique 5 · Tricky
Hidden pair
Two numbers fit into only two cells of a row, column or box. Those cells are now reserved for them, so every other note in the two cells can go. Harder to spot than a naked pair, because the other notes hide it.
- Write your notes. Fill in every candidate of one row.
- Two numbers, two cells. The 6 and the 9 fit into the same two cells and nowhere else here.
- Clear those two cells. They are taken by 6 and 9, so every other note in them goes. Now it is a naked pair.
Technique 6 · Devilish
X-Wing
Pick one number. If it fits into just two cells in each of two rows, and those cells line up in the same two columns, the number is boxed in: it leaves the rest of both columns. Swordfish is the same idea with three rows.
- Two rows, two spots for the 7. In both rows it fits into only two cells, and they sit in the same two columns.
- One diagonal or the other. Either way, each of the two columns gets its 7 in one of these rows.
- Cross it out. No other cell in those columns can hold a 7.
Technique 7 · Devilish
XY-Wing
Three cells with two notes each: a pivot and two wings it can see. Whatever the pivot turns out to be, one of the wings gets the shared number, so any cell that sees both wings can drop it. XYZ-Wing is the same trick with three notes in the pivot.
- Find the pivot. A cell with just two notes: 5 or 1.
- Add two wings. It sees one cell with 5 or 2 and one with 1 or 2. Whatever the pivot turns out to be, one wing becomes a 2.
- Strike where both wings meet. A cell that sees both wings can never be a 2.
Tip: try the techniques in this order. When you are stuck, scan each number from 1 to 9 across the whole board before you start writing notes: most of the time a single is hiding somewhere. The patterns only pay off once your notes are complete.
Solutions
Stuck on a level?
Every level has its own solution page, free and Pro. You see the puzzle first, reveal one number at a time, and open the whole grid only if you want to.
FAQ
Sudoku questions, short answers
What are the rules of Sudoku?
Fill the 9×9 grid so that every row, every column and every 3×3 box contains the numbers 1 to 9 exactly once. The given numbers stay as they are.
Can I look up the rules during a round?
Yes. Tap the gear at the top left of the round: Settings open, and their Game guide row takes you straight to the rules of this game, what is special in it and how the stars work. You also find the guide behind the ? on the level start and in Settings on the home screen.
Where do I start a Sudoku?
Start with the rows, columns and boxes that already have the most numbers. Look for cells where only one number fits, and for numbers that fit into only one cell of a box.
Can a Sudoku have more than one solution?
A proper Sudoku has exactly one. Every level in Beasties is checked when it is made: one solution, reachable by logic, no guessing.
Do I need to guess in hard levels?
No. Even Devilish levels can be solved by logic alone, though they ask for patterns like X-Wing or XY-Wing. Beasties never ships a puzzle that needs trial and error. If you feel you have to guess, complete your notes and look for pairs first.
What is an X-Wing in Sudoku?
A pattern for one number: in two rows it fits into only two cells each, and those four cells form a rectangle. Each of the two columns must then get the number in one of those rows, so it leaves the rest of both columns. In Beasties you need it from Devilish on.
Is level 37 the same for everyone?
Yes. The levels are fixed and come with the app: the same puzzles in the same order for every player. New levels are only added at the end.
What happens after three mistakes?
The level is lost and you start the same puzzle again. Stars from earlier levels stay yours.
Does Beasties need the internet?
No. Beasties works completely offline, and there are no ads.