Il est en première. Do not underestimate the french education system ;) What you need for such a game are Pythagorean and Thales's theorems. I gave him hints so

Il est en première. Do not underestimate the french education system ;) What you need for such a game are Pythagorean and Thales's theorems. I gave him hints so that he poses the problem correctly, but he came up with the formula for moving the red square on his own!