Review deck
425 cards drawn from every lesson, word list and character page on the site. You get 15 new ones a day, in course order, and each one comes back just before you would have forgotten it.
Progress is kept in this browser. Clearing site data clears the deck, and accounts that would carry it between devices are not open yet.
How the timing works
The deck uses SM-2, the algorithm behind most spaced repetition software. Each card carries an ease number. Grade it well and the gap until you see it again multiplies by that ease; grade it badly and the card resets to tomorrow and its ease drops a little. Over a few weeks the deck quietly sorts itself into the words you find hard and the ones you do not.
Grade honestly, especially on tones
If you had the meaning but the wrong tone, that is Again, not Good. A word with the wrong tone is a different word, and grading it as known is how learners end up fluent and unintelligible.