I played around 18,000 quiz duel rounds with my mum across 12 years on QuizDuel. Then I noticed something quietly damning: neither of us actually got smarter.
I'm David Moosmann, founder and sole developer of LearnClash, a competitive learning app where 1v1 quiz duels feed a 3-stage spaced-repetition system. I built it solo at Pluxia GmbH in Baar, Switzerland, and shipped version 1.0 on iOS and Android in September 2025. No ads in any tier.
Below: what I work on, why I built LearnClash, the company behind it, and how to reach me. Or jump straight to a 3-minute duel.
I build LearnClash end to end: product design, mobile app, backend, marketing, and every blog article on this site. The technical stack is Flutter 3.41 with signals.dart on the client and Firebase Cloud Functions plus Firestore on the backend. Four areas take most of my hours.
How spaced repetition, retrieval practice, and difficulty calibration actually move long-term memory. LearnClash uses a 3-stage Mems system: a missed question returns in 7 days; pass that and it returns in 90 days; pass that and it exits the active pool. Plain, not pretty, and it works.
Flutter 3.41 with signals.dart for fine-grained reactivity, Firebase for auth and storage, Cloud Functions v2 for AI question generation. Solo full-stack, which forces ruthless prioritization.
ELO matchmaking adapted from chess, with K=40 for new players (first 10 duels) and K=20 once your rating settles. Eight tiers from Iron to Phoenix. The goal is balanced matches inside ±80 ELO so duels feel earned, not random.
Most of LearnClash was shipped with a paired AI at every step, which the indie crowd calls vibe coding. Used right, it lets a single founder ship in months what used to take a small team. Used wrong, it ships hallucinated code at unprecedented velocity.
I built LearnClash because 12 years of daily QuizDuel rounds with my mum proved one thing about quiz games: they test what you already know but they do not actually teach. LearnClash is the version of QuizDuel I wished existed, where competition feeds a real spaced-repetition system instead of a leaderboard.
Around 2012 my mum got hooked on QuizDuel. So did I. We played daily, every breakfast, every commute, every late evening. Geography, history, science, sports, mythology, pop culture. After a few months the duels became our shared ritual.
By 2024 we had played for 12 straight years. And here is the awkward part. She still missed the same Saturn-moon question. I still missed the same Hungarian river. The duels were fun, the streaks were satisfying, but the learning was close to zero. We had spent thousands of hours testing what we already knew.
The wedge was simple. Take the 1v1 duel mechanic that hooked us for 12 years, layer real spaced repetition into every mode, and use ELO so matches stay balanced rather than random.
She still misses the Saturn-moon question, but at least she now sees it three times a week until it sticks.
April 2026 first-hand observation: across 50 head-to-head test sessions I ran on Sway and LearnClash with my mum, she retained 81% of LearnClash questions a week later versus 23% of Sway's. The difference is the SRS layer, not the question quality.
I write every article on the LearnClash blog myself. As of April 2026 that is 60 posts across three clusters: comparisons (LearnClash versus Quizlet, Kahoot, QuizDuel, Trivia Crack and others), trivia question packs (34 themed lists), and learning-science deep-dives. Three are worth starting with.
The full live distribution of ELO tiers across our player base, retention curves at each Mems stage, and the wrong-answer accuracy gap. Citable numbers, not marketing.
How chess-derived ELO became LearnClash's matchmaking engine, with the actual K-factors, tier thresholds, and why we cap balanced matches at ±80 ELO.
Why the 1-3-7-21 heuristic everyone copies is wrong, how Anki and Quizlet diverged, and why LearnClash uses a 3-stage Mems system instead of the FSRS or SM-2 trees.
I wrote all 60 of them. Browse the blog for the full set.
Pluxia GmbH is the Swiss limited liability company that owns and operates LearnClash. I founded it on December 1, 2023 in the Canton of Zug. Registered office: Blegistrasse 7, 6340 Baar. UID: CHE-198.527.946. Sole director: me.
Full company page with brand assets and press contact: About LearnClash. Legal filings: Impressum.
I'm easiest to reach on LinkedIn for professional inquiries, X for short LearnClash product updates, and Quora for reader questions about quiz apps and learning science. Press inquiries about LearnClash or Pluxia GmbH go to press@learnclash.com; product or support questions go to support@learnclash.com.
David Moosmann, founder and sole developer at Pluxia GmbH in Baar, Switzerland. LearnClash launched in September 2025 after 12 years of daily QuizDuel rounds with his mother revealed that quiz apps test knowledge but rarely teach it.
Yes. David Moosmann designed, coded, marketed, and shipped LearnClash solo using Flutter, Firebase, and AI-assisted development. He runs the operating company Pluxia GmbH from Baar, Zug, Switzerland.
Twelve years of daily QuizDuel rounds with his mum. After roughly 18,000 rounds they realized neither had actually retained much. LearnClash combines competitive 1v1 duels with 3-stage spaced repetition so every question played builds lasting memory rather than just testing it.
Software developer and German national, listed on Wikidata as Q138771338. Specializes in Flutter mobile development, learning-science systems, and AI-assisted coding. Founder and sole director of Pluxia GmbH (Switzerland), developer of LearnClash (Wikidata Q138771266).
Press inquiries go to press@learnclash.com. Product and support questions go to support@learnclash.com. He answers reader questions on Quora as David-Moosmann-2 and posts product updates on X as @damoosmann.
Free to play. No ads. No credit card.
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