Equation Challenger

Equation Challenger is a simple, offline mental-math game that sharpens addition skills in a few minutes a day. HOW IT WORKS You are given a target number between 20 and 99. Tap two digits on the on-screen keypad that add up to that target. For example, if the target is 47, tap 2 then 5, or 1 then 6 — anything that equals 47 when summed. The answer field turns green when you are correct and resets to a new target. If your sum is off by 10 or more, or if your first digit leaves no valid second digit, the field turns red and a new target appears so you can keep the pace up. WHAT IT IS GOOD FOR • Daily mental-math warm-up for kids learning addition • Quick brain break for adults • Speed drills — the game resets fast, so you get many reps per minute • A calm, low-stakes alternative to timed math flashcards DESIGN PRINCIPLES • Completely offline — no internet connection needed • No ads • No analytics, no tracking, no third-party SDKs • No accounts, no sign-in, no personal data collected • No in-app purchases • Minimal Android permissions — nothing sensitive is requested • Safe for children: compliant with COPPA and GDPR-K by design WHY IT IS SAFE FOR KIDS The app runs entirely on your device. It has no network access, no ads, and no way to contact the outside world. Nothing you do in the app leaves the phone. There is no profile, no leaderboard, no chat, and no link to external websites from inside the app. HOW TO PLAY 1. Look at the target number shown on the right of the screen. 2. Tap the first digit (the tens digit of your first addend). 3. A + symbol appears. Tap the second digit (the tens digit of your second addend). 4. When the two two-digit numbers sum to the target, the display turns green. 5. A new target appears. Keep going. TIPS • Think in pairs that sum to 10 first (1+9, 2+8, 3+7, 4+6, 5+5), then adjust the tens. • Aim for consistent speed, not perfection. Red answers are fine — the next round starts immediately. ABOUT Equation Challenger is a small, open-source-style personal project built by Fominykh Maksim. It is free to use forever, without ads and without tracking.