# Flashcard site built (Leitner spaced repetition) over the full glossary

User requested a flashcard site for repetitive drilling of glossary terms. Built `reference/flashcards.html` with the Leitner system (5 boxes, doubling intervals: Box 1 every session, Box 2 every 2nd, Box 3 every 4th, Box 4 every 8th, Box 5 every 16th).

Mechanics: progress persists in `localStorage` (key `design-flashcards-v1`); three modes (term→definition, definition→term, mixed); filter by lesson tag (L0001, L0003, L0004, untagged); keyboard shortcuts (Space=flip, 1=miss, 2=got it). Click-to-flip card with CSS 3D transform.

Deck currently holds 25 cards (4 CRAP + 6 hierarchy + 10 typography + 5 untagged). When the glossary grows in future lessons, append matching entries to the `DECK` array in `flashcards.html`. New IDs auto-backfill into Box 1 on next load.

Signal: this user values spaced retrieval tooling, not just drill lessons. When introducing new vocabulary in future lessons, plan to add the matching flashcard entries in the same change.