Missing Numbers Minds

Improve your mind skill finding out the missing number.
Choose the up to 10 levels: Easy, Medium, Hard , ( linear, recurrence or both ) or Random.
Push START- Time Up or Time Down
Guess the missing numbers to get points. Higher Level , more points.
Ideal for kinds and people who need to exercise their brain.
Very easy to use.
Donations for App maintenance welcome.
Thanks.