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21st NIM

Programs require a Java enabled browser. With the latest Java 7 Update 51, you may need to add to the "Exception Site List" on the Security Tab of the Java Control Panel and change the security level from "high" to "medium" only if you still have a problem. How To access the Java Control Panel. Click on the Security Tab and move the slider to Medium, this will allow the puzzle applet to load with security prompts. You can also add to the Exception Site List while on this same tab. Click Apply and then click OK. More help
Click on a version below to play

Ahhhhhhh, no JAVA !


This game rules are very simple: two players alternatively remove from one or more balls from a selected pile. Remember a player can also remove all of the balls in a pile during their turn. The winner is one who removes the last ball.


Click on* on the following buttons to play

  • "New Game" button - restarts the game
  • "Start Game" button - starts the game
  • Arrow button in lower right part of game to select oppenent   and number of piles:

    - computer opponent, with computer having the first move
    Computer(2) - computer opponent, with computer having the second move. You will move first
    Player - opponent is human being

    Number of piles
    Click on the arrow button and select the number of the piles (2-9). Each pile will be filled with a random number of balls (1-9)


  1. Move your curser over a pile. Clicking on* a pile will change the outline color of the pile from yellow to green.
  2. Press "Take Ball" button, once for each ball you want to remove. You must remove at least one call. Balls can only be removed from one pile during each turn.
  3. After you have removed the desired number of balls from the pile click on "Change Over". This allows the next player to play. If you remove the last ball from a pile the automatic change over is performed for you. The computer opponent automatically click the change over button after move.

Beginners should begin with the computer moving second and one pile. To increase difficulty change to the computer moving first and increase the number of piles.

Back up moves (reverse).

Look at the game as a subtraction game.


Nim is thought to have originated in China, but the name is thought to be German from nimn the German word for take. The first European reference to the game is in the 15th century.  

Algorithm for this game was prepared still in 1902. by Charles Bouton, a Harvard University mathematician. Originally it was known as Nim (probably per german word nimm (take).

Click on*