(Open Source) Mental Math

A free, open-source mental math trainer. No ads, no paywalls, no locked content — every exercise and difficulty is included. Sharpen your arithmetic with quick timed tests, custom drills, and a library of mental-math tricks. Everything runs offline and your progress stays on your device. FEATURES Timed Tests A daily 60-second challenge plus sprints, a two-minute marathon, per-operation tests, and a hard mixed test — at four difficulty levels, each with best scores. Custom Trainer Pick a number domain (Times tables, Natural, Decimal, Money, Huge), choose one or more exercises, and set per-exercise difficulty from Easy to Super hard. All the Operations Addition, subtraction, multiplication, division, squares, square roots, fractions, percentages, and modulo. Mental Math Tricks Dozens of step-by-step tricks for faster addition, subtraction, multiplication, division, and squares — with worked examples and favorites. Practice Any Trick Every trick comes with a 60-second drill built for it: × 11 drills, squares ending in 5, numbers near 100, and more. Magic Square A number puzzle: make every row, column, and diagonal add up to the same total. Four levels, from 1-9 up to bigger number sets. Progress Tracking Solved totals, accuracy, best run, daily streak, longest streak, and a weekly activity view. Fast Sessions An on-screen keypad with instant answer checking and haptics. No ads. No paywalls. No account required. 100% Open Source The complete source code is public - see it, audit it, or contribute at https://github.com/Open-Apps-Studio/mental-math