Every new word and every mistake feeds a smart review queue (SM-2 spacing). Review rounds mix multiple choice, listening, translation and fill-in-the-blank — 10 items a session. Reviews never cost hearts.
A freeze auto-consumes if you miss exactly one day — it can't save a longer gap.
Clears XP, streak, hearts, gems, crowns and the review queue on this device. PocketBase (Word Bank) history is untouched.