Here's a nicely made online free sudoku game. This game follows the standard rules of sudoku.
To begin, click the Small, Medium, or Large link or Very Large button under the picture at left. This opens the game in a pop-up window.
The HTML5/Mobile version works on desktop computers and tablets. It is a similar game made by a different game developer.
Use your powers of logical deduction to determine the numbers missing from each row and column.
Note: If you want to print out sudoku to solve with pen or pencil, see my 100 Free Printable Sudoku Puzzles page.
HOW TO PLAY. In standard sudoku (including this online game), you are presented with a 9 by 9 grid divided into 9 three-by-three boxes.
Numbers between 1 and 9 are scattered throughout the grid, with many spaces blank.
The numbers are not scattered randomly. Rather, they are part of a unique solution for the puzzle.
Your job is to figure out the missing digits, keeping the following rules in mind:
The numbers 1 through 9 can only be used once in each row.
The numbers 1 through 9 can only be used once in each column.
The numbers 1 through 9 can appear only once within each 3-by-3 box.
The sudoku puzzle has one unique solution.
To enter a number in the grid, first click the number in the number listing on the left. This highlights the number. Then click the location in the grid where you want that number to appear.
For example, suppose you've figured out that a 5 should be placed in one of the blank squares in the grid. Click the 5 in the number listing, then click the space where you want the 5 to go.
STRATEGIES. There are two basic sudoku strategies I use all the time: 1) the "sure thing", and 2) elimination.
1) The sure thing strategy is easy to perform in an online free sudoku game. To use this strategy, look for situations where it's possible for only a single number to be placed.
Consider the screen image at left. This was taken from the online free sudoku game above.
Notice how I've placed a black 5 in the 3x3 box on the right side of the puzzle. A 5 is the only possible entry for that position.
Why? Because the two red 5's I've circled, plus the existing numbers in the 3x3 box, eliminate all open positions except one.
Remember, according to the rules you can only have one number each between 1 and 9 in each row, column, and 3x3 box.
One of the circled 5's eliminates that row, while the other circled 5 eliminates that column. The box where I entered the black 5 was the only available spot in that 3x3 box.
2) The elimination strategy requires the use of pen and paper, so it's not really conducive to online free sudoku games (at least not this version).
The idea is to figure out the multiple possible entries for an empty square, then lightly pencil in those possibilities. As you work through the puzzle, you figure out which numbers are the actual solution.
If you really want to try the elimination sudoku strategy, you might need to get some blank 9x9 sudoku paper and copy down the puzzle from this online free sudoku game.
Or print out some of my free printable sudoku puzzles.
OPTIONS. This online free sudoku game includes a couple of options.
Timer. The first is the timer, in the upper left corner. The timer is really only needed if you're interested in keeping track of how fast you solve the sudoku puzzles.
Buzzer. If you make an incorrect entry in the grid, a buzzer sounds and 10 seconds are added to the timer. So it pays to think carefully before you make a move!
Hint. If you get stuck, click the Hint button. This fills the answer in one of the empty squares in the grid (at random, you don't get to choose which one). There is a 50 second time penalty each time you use the Hint feature.
Help. Click the Help button to view a list of sudoku rules.
Sound. To turn off the sound effects, click the speaker button.
Sudoku is one of my favorite number puzzles. I've got Sudoku puzzle books that I often dip into when I feel like solving sudoku on paper rather than playing online free sudoku games. The one by Will Shortz is particularly nice.
If you haven't played much sudoku, I encourage you to give this math puzzle game a chance. It's a fun game that can help keep your brain sharp.
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