How could my project be improved ?

Question

I've released my third project on the Google Store. It is a memory based game aiming at helping children to read numbers. The second aim of this project was to test Google Play features such as Leaderboards... Now I wonder what could I do to improve it further...
Here is the link: https://play.google.com/store/apps/details?id=com.ClemGrt.MemoryDesNombres

I thank all of you in advance for testing, commenting, ranking and rating it 😀

Answer 1

I also post here the links to my two previous projects :
https://play.google.com/store/apps/details?id=com.Memorial.Dice_Roller

https://play.google.com/store/apps/details?id=com.Company.DesDePerudo