Age doesn’t matter when you are talking about a fun puzzle games.
Now to try and describe this game. First of all there is a grid of 15 squares by 15 squares and within these squares they are divided by 3. This helps so with a thicker black line it is easier to count by 5’s.
Each line whether it is diagonally or horizontally will be numbers like 3, 2 which tells you how many boxes you need to chisel in that particular direction. So 3 mean a grouping of 3 and 2 means another grouping of 2 that should not be there.
As you progress through the game the puzzles naturally get harder and larger. The numbers can eventually look like this, 2, 5, 1, 4, 2, 1. You can see that it can get complicated but it is so much fun. I would just turn off the music, but it is up to personal taste on how much tinkling you can take.
Other fun puzzle games of this age are Boxxle and Kwirk.