Invisible Ping Pong vs KnowDown

Invisible Ping Pong lets you play Table Tennis against your friends, using your phone as racket and detecting the swing gesture. You can train against a bot or even challenge your friends in a 1vs1, without the need of a table, an actual racket or even a ball.

Welcome to KnowDown — the trivia game that truly measures your knowledge. Answer more than 3,000 quiz questions across 11 categories: history, science, culture, sports, geography, technology, general knowledge, food, entertainment, mythology and health. Every correct answer raises your ELO rating. Every miss teaches you something new. WHAT MAKES KNOWDOWN SPECIAL • ELO rating system: Your skill is measured like a chess grandmaster's. Beat harder questions, rise faster. Fair, competitive, transparent. • Curated question base: 3,000+ carefully written trivia questions in 11 categories — from everyday knowledge to deeper challenges. Regularly expanded and improved with play data. • Global leaderboards: Compete with players worldwide on a live Top 100 leaderboard. See in real time who's pushing for the top spot. • Smart matchmaking: Questions adapt to your ELO. Beginners get easier ones, experts get challenged. • Daily limit: 10 questions per day keep you coming back — no pressure, no burnout. • Friend-code bonus: Invite friends with your 8-digit code. You get +1 question per day for 7 days per invite, your friends get +2 questions per day for 7 days. • Day streaks & awards: Play every day and build your streak. Unlock achievements for streaks, perfect days and ELO milestones. • Answer history: Review every question you got right or wrong — and learn from it. • Dark & light theme: Easy on the eyes, day or night. HOW IT WORKS 1. Create your account via magic link (e-mail) 2. Answer up to 10 questions per day 3. Earn ELO points for correct answers 4. Build your day streak and collect awards 5. Climb the global leaderboard ACCESSIBILITY IN FOCUS KnowDown was built with accessibility in mind — the developer is visually impaired and uses VoiceOver every day: • Optimized for VoiceOver and TalkBack • Improved contrast and larger touch targets • Adjustable text sizes and reduced motion • Important information is not conveyed by color alone PRIVACY & SECURITY • Passwordless login — no password to leak • No third-party trackers, no ads, no data selling • Hosted in Germany under German law Questions? Feedback? Get in touch: support@knowdown.de KnowDown — Think fast. Score higher. Come back tomorrow.