Sudoku with wooden pieces - Two in one, numbers

The mathematical puzzle called «Sudoku» originates from Japan. It has gained widespread popularity around the world due to its engaging nature.
The tabletop game for toddlers Sudoku «Two in one, numbers» with wooden pieces is an extremely captivating and interesting puzzle... that will appeal to both children and their parents. The game is also great for school preparation.
 
Game components:
• wooden pieces with numbers - 81 pcs (1.7 x 1.7 cm);
• double-sided game board - 1 pcs (20.5 x 20.5 cm, cell size 2 x 2 cm);
• instruction with tasks and answers - 1 pcs (a total of 20 tasks of varying difficulty).
 
How to play?
The tasks presented in this game have different levels of difficulty. Each task has a single correct solution.
A simple puzzle with a large number of filled cells can be solved in a few minutes.
A complex one, with a small number of digits placed, can take several hours.
 
The first ten tasks are played on a 6 x 6 cell board. Tasks from the eleventh to the twentieth are on a 9 x 9 cell board.
 
At the beginning of the game, numbers - «hints» are placed in the cells of the board corresponding to the tasks. You need to fill in the remaining empty cells with the missing numbers.
 
This should be done so that the numbers do not repeat:
in each column,
in each row,
in any of the small squares.
 
At the end of the instructions, answers to all the tasks of the puzzle are provided.
    
Solving the tasks contributes to the development of attention, memory, spatial and logical thinking. Additionally, the child will practice perseverance and the skill of solving problems independently.