I started to create a game to help my son learn basic math the fun way.
Addition, Subtraction, Multiplication and Divding with numbers of different length can be trained.
For gamification, there is a score tracked and a leaderboard.
I’d call it 80% done, so it can be used already but some tweaks are missing to make it a flawless experience.
If it’s completed and there is interest, I might do an English version as well.
Give it a try if you like and leave some feedback 
Things on my list
- create a difficulty function to scale the score according to difficulty
- prevent negative numbers / make that an option as well
- allow showing the leaderboard from the options screen
- hide life and score header when going back to the main menu
- prevent duplicate answers
- make wrong answers be closer to the right answer
