Sudoku, by Lottery Post

Sudoku is a logic game that in recent years has become one of the world's popular puzzle games, appearing in most daily newspapers and in scores of paperback books.

Lottery Post has created a special online version of Sudoku that, unlike a book or newspaper, has the benefit of a virtually unlimited number of game board variations.  However, if you have a more challenging Sudoku puzzle from another source, you can enter the numbers on the Sudoku playing board above, and play the puzzle online!

The Sudoku puzzles created by Lottery Post are generated on-the-fly (right as you press the button), so you will not find these puzzles anywhere else!

Each puzzle created by Lottery Post is:

• Unique and with just one solution — all important as you'll only want to play a game of Sudoku knowing that it is constructed correctly.
• Graded in difficulty — you can generate puzzles according to your abilities: easy, medium, or advanced.
• Symmetrical — Sudoku devotees demand puzzles that are elegant in design, and not just a random set of numbers thrown onto the playing board.

Of course, every serious Sudoku player needs to know the length of time in which they were able to solve the puzzle, so we have included a timer as well.  Pause and Reset controls are provided, so you can put the game on hold while you step away from your computer, or you can start over.

You never need to worry about leaving the page and losing your game.  A special feature silently and automatically saves your playing board if you navigate your web browser away from the Sudoku page, or if you reload/refresh the page.  When you come back to the page, the saved board is restored, and the timer begins right where it left off.

How to Play Sudoku

1. The game board is a 9x9 grid of cells.  You will notice that the board is further divided into 9 separate 3x3 boxes.
2. The object of the game is to fill every cell on the playing board with the correct numbers.  The puzzle is solved when all of the cells are filled.
3. Each row in the game board must contain all of the digits 1-9.  Each digit must appear just once.  For example, you cannot have the digit 9 appear twice in the same row.
4. Each column must contain all of the digits 1-9, and can only contain one of each digit.
5. Each 3x3 box must contain all of the digits 1-9, and can only contain one of each digit.
6. When you start the game, an initial set of fixed numbers is placed on the playing board, and these numbers cannot be changed.  (Fixed numbers are green in color.)  You need to use the logic of the three restrictions above (rules 3-5) to decide what values the empty cells can take.  The initial numbers are chosen such that there is only one correct solution to the puzzle.
7. The game will prevent you from entering a number that is clearly wrong, such as entering a second 9 digit in the same box.  However it will let you enter wrong answers that still fit with the visible digits, so be careful when choosing your numbers!  Seasoned Sudoku players know the feeling well of getting near the end of the puzzle, and realizing that one of the numbers entered early on is wrong.  That is part of what makes the game fun and challenging.

Controls

• The playing board has a special highlighted cell, called the cursor.  To place a number on the playing board, move the cursor to the cell in which you want to place the number, and enter the number using either your keyboard or your mouse.
• Cells with green numbers are locked and cannot be changed.  Black numbers can be changed by you.
• Keyboard — Use the four arrow keys on your keyboard to move the cursor.  Place a number on the playing board by pressing a number key on your keyboard (1-9), or by pressing a letter key (A-I, where A=1 and I=9).  Clear the number in the cell by pressing the space bar, Delete key or Backspace key.
• Mouse — You can use your mouse to click any cell to instantly move the cursor to that cell.  Insert a number in the cursor cell by clicking the numbered button on the control pad on the right side of the playing board.  You can clear a number by clicking the blank button next to the numbered buttons on the control pad.
• Combination — You can use both the mouse and keyboard together if you like.  For example, use the mouse in one hand to move the cursor quickly to a cell, and press the number you wish to insert with your other hand on the keyboard.
• The large buttons on the control pad perform the following functions:
  • Create — Creates a new game board filled with a randomly-generated numbers.  The game system tests to make sure that only one solution exists, and that it is indeed possible to solve the puzzle.
  • Hint — Suggests a cell that the game system thinks will be relatively easy for you to find the correct number.  Examine the box, row, and column around the hinted cell to find the correct number.
  • Solve — Displays the full solution, but only if you press and hold the button down.  As soon as you release the button, the solution disappears.
  • Reset — Resets the board to the initial configuration, by removing all the black (unlocked) numbers.
  • Clear — Clears all of the numbers from the game board so that you can enter a puzzle taken from elsewhere.  For example, you can play a Sudoku game from your newspaper by pressing Clear and then copying each of the numbers into the corresponding cells.  See Lock below for more on this topic.
  • Lock — Locks all of the numbers currently on the game board so that you don't change any of the numbers accidentally.  If you entered numbers from a game board you found elsewhere (see Clear above), you can use the Lock button to freeze those numbers once you finish entering them.

Technical Requirements

Lottery Post's Sudoku game requires a modern web browser and operating system.  Creating the game's features and fast performance required the use of technologies that are only found in more recent products.

The minimum requirements for using Lottery Post's Sudoku game are as follows:

• Modern operating system, such as Windows 10, Windows 7, or Mac OS/X.  Windows Vista, Windows XP, Windows ME, Windows 98, and other lower varieties are not supported.
• Modern web browser, such as Microsoft Edge, Google Chrome, Firefox, Safari, or Opera.  Your brand and version number of web browser is the most important factor in determining if you can play Lottery Post's Sudoku on your computer!  Web browsers like IE7, Internet Explorer for Mac, and all other older web browser varieties will not work with Sudoku.
• JavaScript enabled.  JavaScript must be enabled in your web browser for the game to function at all.  To enable JavaScript in your web browser, see your web browser documentation, or check out Lottery Post's help guide for enabling JavaScript.
• Cookies enabled.  Cookies must be enabled in your web browser if you wish to have your game board automatically saved when you navigate away from the Sudoku page.  If cookies are disabled or blocked, the rest of the game will still work fine, but you will lose your game if you go to a different page or if you reload the page.  To enable cookies in your web browser, see your web browser documentation, or check out Lottery Post's help guide for enabling cookies.
• Monitor resolution of 1024x768 (or greater).  If your computer monitor supports only a lower resolution such as 800x600, or if your browser window is not maximized, then the right side of the playing board may be cutoff.

Overall, any web browser configuration that passes all of the Lottery Post compatibility checks should work just fine.  You can go to the Browser Compatibility Test page to see if there are any problems with your setup.