Number Place

Number Place is the nine-by-nine number puzzle many people know from newspapers. You fill a grid with the digits 1 to 9, and every puzzle here can be solved by careful thinking alone.

How to play

Some squares are already filled in. Your job is to fill the empty ones so that:

• every row holds the numbers 1 to 9 exactly once,
• every column holds the numbers 1 to 9 exactly once, and
• each of the nine three-by-three boxes holds the numbers 1 to 9 exactly once.

To place a number, tap an empty square and then tap a number under the board. Tap the same number again to take it out. The starting numbers cannot be changed. When you select a square, the game shades its row, column and box, and it highlights squares that break a rule so that you can see a mistake early.

Pencil marks help when a square could hold several numbers. Turn on Notes, and the number buttons write small notes in the square instead of a real answer. Erase clears a square, and Undo takes back your last step.

On a computer, you can also use the keyboard. Press 1 to 9 to enter a number, Backspace, Delete or 0 to erase, N to switch Notes on and off, and the arrow keys to move between squares.

The Hint button points to a square you can fill and tells you why that number belongs there. The reasons are the same ones you would use yourself, so Hint also works as a lesson.

The levels

The levels depend on which solving techniques a puzzle needs. They were graded by a program that solves puzzles the way a person does, and puzzles that would need guessing were left out.

• Easy: only simple steps, where a square has one possible number. These puzzles start with at least 34 numbers filled in.
• Medium: fewer starting numbers, between 27 and 33, or a puzzle that needs a little more thought, such as noticing that a number must sit in one row of a box.
• Hard: needs matching pairs or triples, where a few squares share the same few candidates.
• Expert: needs advanced patterns such as X-wing, swordfish or XY-wing. You get 3 hints.

On Easy, Medium and Hard, Hint is unlimited.

Today's game

The daily game is a Medium puzzle. Everyone who plays on the same calendar day gets the same puzzle, chosen from the list of graded Medium puzzles.

Tips

1. Pick a number and look at where it already stands. Its rows, columns and boxes are closed to it, and often only one place is left.
2. Look for a row, column or box that is nearly full. The last missing number is easy to find, and each one you fill helps its neighbors.
3. Count the numbers in each box. A box with many numbers is a good place to start.
4. Use Notes when a square could take two or three numbers. Cross them off as you learn more.
5. If two squares in a row both can only be a 3 or a 7, those two numbers cannot go anywhere else in that row. This is the idea behind pairs.
6. Do not guess. If you feel the need to, you have probably missed a note or a clue, so look again, or ask for a Hint.
7. Take breaks. A fresh look often shows the one square that was in plain sight.

A bit of history

Number puzzles with this grid spread from Japan to newspapers around the world and became a daily habit for millions of people.

Questions

Does every puzzle have only one answer? Yes. Each puzzle is checked so that exactly one solution exists, and it can be found by logic.

Why is a square marked? The same number appears twice in a row, column or box. One of the two is wrong.

What do the Notes do? They are small pencil marks for you. They do not count as answers, and you can turn them off at any time.

Can I make a mistake and not know? The game highlights clashes, but a wrong number that does not clash yet can stay hidden. Use Hint if you feel unsure.