Flashcard Spaced Repetition App

A real spaced-repetition app, not a random quiz. Implements the actual SuperMemo SM-2 algorithm: ease factor, interval growth, lapse handling, computed exactly per the classic formulas. Multiple decks, due/new counts, a focused one-card study flow, streak + retention stats with a hand-drawn SVG ring, 2-step delete confirms, JSON export/import. Zero dependencies, fully offline. Playwright-verified: every demo card matches an independent SM-2 re-simulation. (AI-assisted build; verified working.)