Worldsong
Learn the countries of the world
A growing arcade of learning games
Games kids beg to play. Learning that actually sticks.
Mastery Arcade is a growing arcade of learning games, powered by real learning science. One pass unlocks every world — and behind the fun, the same proven engine makes what they learn last.
The lineup
One pass, every world
New games arrive over time — your access comes with them. Times Machine is live now; Worldsong is on the way.
The moat
Real learning science, behind every game
The fun is the disguise. Under every Mastery Arcade game runs one shared engine — fifty years of research, working the whole time.
Spaced repetition
The right fact at the right moment
Every fact resurfaces right before a kid would forget it — the inflection point of the forgetting curve, computed per fact, per learner. That's when re-learning locks in, so practice time is never wasted.
Fluency, not just correct
Fast enough to be automatic
Speed of recall — not just accuracy — predicts long-term success. We time every answer against an age-tuned threshold, so a kid who knows it cold is graded apart from one who's still calculating.
Cover-Copy-Compare
Miss it, then earn it back
On a miss, the answer flashes, vanishes, and the kid retypes it from memory. Active retrieval beats passive correction by a wide margin — and it fires automatically, every time.
Mastery ladder + boss gate
You only advance by truly mastering
Progress is gated on real fluency, not effort. The boss fight is a hard gate — you win only by answering every fact correctly and fast. No shortcuts, so what kids unlock, they own.
Who it's for
Built for the people around the kid
For families
See progress at a glance — what each kid has mastered, where they're stuck, and a streak that keeps them coming back. The rare app where kids ask to practice.
For classrooms
Fluency practice the whole room actually wants to do, with a class dashboard for oversight and none of the busywork. Roster in, playing in minutes.
Start playing
Make practice the part of the day they look forward to — and watch the skills stick.