"Review only" mode. A quick session that serves ONLY the previously-missed cards, so Benjamin can drill through his weak spots.
Progress stats per category. The current stats block totals across the whole pool; a per-category breakdown ("math: 48 seen, 6 missed") would help track weak areas.
Spaced-repetition scheduling. Currently "right" cards cool down for a fixed 30 marks. A Leitner/Anki-style schedule (each correct answer lengthens the cool-down; each miss resets it) would be more powerful.
Streak tracking. Log per-session totals over time; celebrate 5-in-a-row or 10-in-a-row streaks.
Audio read-along. Optional text-to-speech reads the question aloud for hands-free bedtime play.
More cards. 600 is a lot, but with nightly use he'll cycle through in a couple of months. Room to keep growing.
Uplink-editable question submissions. Same pattern as the other games — you or Benjamin could submit new Q/A/why entries via the existing uplink form.
Difficulty auto-tuning. If he's crushing every "easy" card, silently retire the trivial ones instead of showing them again.
Print-friendly deck view. A /print page that lists all questions in a booklet layout for offline use in the car / on a plane.
Known constraints / by-design
Data is per-browser (localStorage). If you play on the phone and the laptop, they're separate progress logs. Cross-device sync would need the Supabase pattern from the other games.
Every answer is self-graded (or parent-graded). No fuzzy text matching — Q55's answer "Seven" would trip up a typed-answer system anyway, and Brain Quest's whole gimmick is verbal check-yourself.
Category tag for Arts covers arts + logic + riddles collapsed into one bucket. If the corpus grows big enough to warrant splitting them later, easy to move IDs.