Spaced Repetition · Recall · Mastery
Small tools that make big subjects stick. Every volume below runs on spaced repetition, so most of your practice lands on whatever you know least.
How the drills workA Note from the Librarian
Every answer feeds a schedule. Miss a question and it comes back within a round or two; get it right and the wait grows each time. Most of your practice lands on whatever you know least, which is the point.
An item counts as mastered after five correct answers in a row, each one quick and unassisted. Master everything in a set and the round ends. If you miss a mastered item later, it goes back into rotation.
Most drills come in pairs. You can hunt for a country on the map, or see it highlighted and type its name. A fact learned both ways is harder to lose. Hints help when you're stuck, but a hinted answer doesn't count toward mastery.
Each tool keeps a small tally while you play: your streak, this session’s correct answers out of questions asked, and how much of the set you’ve mastered so far. All of it saves to your browser and nowhere else.
Type Invaders plays by arcade rules but studies you all the same: word packs drill the letters that slow you down, and the flag and constellation packs run on the Library’s spaced repetition — Study Hall included.
The Pocket Edition
Some of what’s on these shelves also comes as ready-made flashcard decks for Flickdeck, a calm spaced-repetition app for iPhone. Flags, constellations, world capitals, and more — browse the deck library, tap one on your phone, and it opens straight into the app.