Logic Masters Deutschland e.V.

I’ve always found complete blank puzzles particularly charming. But figuring out how to break the symmetry so that the puzzle has a unique solution is a challenge.
In my anothe puzzle, I tied the center cell of the box to the box number to break the symmetry.
For this puzzle, I've come up with an even smarter idea.
It might have a tough start, but it ends beautifully.
Have fun!



Rules：
Fill in the digits 1-9 in each row, column and box without repetition.
When a digit in a cell matches the number of its row, column, or box, we call that cell a friendly cell. There are 15 friendly cells in this grid， find them out.
The difference between any two orthogonal adjacent digits is at least 3.
The digits of the same position in each box is unique.

Click the image to play.↓↓↓