Mental arithmetic practice on a tablet, for children from their first school year. The app measures the time to the correct answer and turns it into a learning curve and leaderboards, where several children on the same device compete with each other. <b>The interface is in German only.</b> It runs entirely offline. No account, no ads, no analytics and no internet permission - the app cannot send anything anywhere. <b>76 lessons in nine groups</b> Counting and comparing pictures for the youngest, then addition and subtraction up to 10, 20, 100 and 1000 - with and without carrying - the times tables forwards and backwards, division with and without a remainder, order of operations, telling the time and handling money. <b>Stars for care, lightning bolts for speed</b> Two separate axes on purpose. Stars follow the error rate, bolts the time per task. A child who works carefully earns the stars even slowly. <b>What parents can set</b> Behind a PIN: which groups a child is offered at all, how long they may practise in one stretch and per day, how many runs of one lesson still count towards records in a day, and whether difficult tasks are woven back in. Assignments too: give a child a lesson, daily or weekly, or as a plan for one named day, with a minimum of stars and bolts to reach. <b>Your data stays with you</b> Everything lives in a database on the device. A backup is written only when you ask for one, and handed to Android's share sheet - where it goes is your choice.