Wonderdex

Every card starts with something that sounds wrong. Why does a bike stay up on its own? Not gyroscopes. Why do astronauts float on the space station? They're not "outside gravity." Wonderdex has 1,250 cards across physics, math, chemistry, geography, and history — each one built to make you guess before it tells you why. 364 of those cards exist just to take apart ideas that get repeated as fact, including the textbook explanation for how wings generate lift. Every card links to a real source — a textbook, a university, a government agency, a peer-reviewed publication. Any number gets checked against two independent sources before it's allowed in. If a fact doesn't hold up under that, it doesn't ship. This isn't a quiz app, and it isn't a textbook. It's a curiosity map: 1,250 cards tied together by 3,616 shared-topic links, so a fact about friction can lead to one about tectonic plates, which leads to one about the Cold War. Follow the thread as far as you want to go. Cards are leveled from elementary through university-challenge, so the same deck works whether you're in Grade 6 or Grade 12 — pick a level and start pulling threads. No ads. No accounts. No in-app purchases. No data collected, ever. Everything works fully offline — as good on a plane as it is on the couch. What's inside: • 1,250 fact-checked cards across physics, math, chemistry, geography, and history • 364 myth-busting cards, including the textbook wing-lift explanation, the bicycle-gyroscope claim, and "there's no gravity on the space station" • Every card cites a clickable source: textbook, university, government agency, or peer-reviewed publication • Numbers cross-checked against two independent sources before publishing • 3,616 topic-to-topic connections to explore • Five reading levels, elementary through university-challenge • Fully offline, no ads, no accounts, no tracking Wonderdex is for anyone who's ever thought "wait, is that actually true?" — and wants an answer they can check for themselves.