Fill in the digits 1 to 9 in a 9x9 field in such a way that every digit only occurs once on a row, a column, and in one of the 3x3 blocks.
Various difficulty levels, but need to pay for the most difficult puzzles.
It is only Sudoku puzzles, so variation is just in the starting digits.
Looks simple but functional, certain things like the way digits are marked when all are filled in can be a but distracting at first.
Quite some functionality is hidden behind a payment wall.
I give Good Sudoku 6 out of 10 stars. Feels more like a tool to help you solve Sudokus.