Falcon Sudoku

Intro about the game: Falcon Sudoku is a falcon version of the very famous number game sudoku. Purpose of the game: Just like in all sudoku games our objective is to fill each row and column of 3 X 3 block with all digits from 1 to 9. the squares with numbers already written in them can not be changed. How to play the game: In order to place a digit in a cell we have to click it with the mouse left button to show the digit picker, then we have to click on the desired digit and it will be placed in that cell. Some special tricks about the game play: In case you feel like you have entered a wrong number and it doesn't match the other cells all we have to do is click on that number and that cell will be cleared. In order for us to differentiate between the numbers already written and the numbers added by us the cell background color is dark for the unchangeable numbers and light brown for the empty changeable cells.