how_to_play - rules_of_game
The board has 9x9 squares, divided into 9 areas 3x3 squares each. Squares can hold digits from 1 to 9. Some of them are placed automatically when game starts, placement of the others is the task of the player.
A player’s task is to fill empty squares the board with digits, in a way that in every column, every row and every 3x3 area, each from the digits 1-9 appears exactly once. Player should do that in as short time as possible.
Clinking left or right mouse button on game square one can change digit that is there. Using left mouse button causes digit to increase its value, using right one causes value to decrease. Additionally there exists possibility of using mouse dragging to move digit from one square to another. In case of dragging, if destination square is already occupied, values of two squares (source and destination) are exchanged. Digits can also be entered using keyboard - it is enough to move mouse cursor over square of interest and press the right key. In order to remove once entered value from board, it is possible to simply press Delete or Backspace key.
Player's score is the time player needed to finish the game - the shorter the better.
Below you can see example board exactly at game start, before any digits are entered by the player:
After the board is filled correctly, board looks like this:
The game is over the moment when all squares on the board are filled with digits and there are no conflicts between them (in every column, row and 3x3 area every digit appears exactly once).