Small point of criticism:
The number space could have been designed more generous (zBbis 50), since some children are safe further in the first class. Just for that I subtract a star. My daughter would certainly take a different decision, because she is still thrilled with the thing and for them the game is after all meant.
All in all, a very meaningful "investment"! Buying apps have also generally has the advantage that the children are not zugebombt with meaningless advertising and thereby come to the strangest ideas ....