Universal Cards.my - my indie iOS vocabulary app

[Cards.my]

I wanted to share something I’ve been building, Cards.my. It's a vocabulary flashcard app for iOS - I started it in early 2022 and have been chipping at it on weekends since.

At its core, it’s still just flashcards:

• folders (topic / level / whatever structure you want)
• word pairs (your language ↔ foreign language, optional images)
• two study modes:
  • Learn: self-paced, reveal/hide, free navigation, shuffle anytime
  • Test: shuffled, typed answers, case-insensitive + trimmed input, instant feedback, no backtracking, final score + retry if performance is bad

Nothing novel there - that part is intentionally boring.
What ended up making it interesting for me were the small «product correctness» details and constraints that stack up over time:

• Pronunciation is fully system-based (AVSpeech). The speaker only appears when iOS actually supports a voice for that language, and the app auto-detects the dominant language per folder so you don’t end up with broken audio buttons everywhere.
• There’s a cross-folder review mode («Words you often forget») that aggregates weak cards across the entire library based on actual performance history, not just per-deck repetition.
• Folders are portable files. You can export a .cardsmy file and send it via AirDrop / Messages / email, and it just imports on the other side. No account needed.
• CloudKit handles full sync, including images.

Stats are intentionally not «streak-based gamification». Instead:

• 7-day practice strip
• mastered / weak word lists
• revisit queue based on real errors
• reminders that adapt to activity instead of nagging for streak preservation

There’s also AI-assisted example generation per card:

• tap “Examples” → generates a few usage sentences for the target word
• strict guardrails (rate limits, quotas, refusal rules)
• explicit “AI may be wrong” labeling everywhere it appears

On the engineering side, a lot of effort went into boring reliability work:

• debounce search everywhere
• undo window for folder deletion (5 days)
• stable sort persistence
• exam hint system
• deep links

And then the AI layer, which turned out to be more prompt engineering + validation than UI work:

• strict JSON schema enforcement
• deduping via normalization (case, whitespace, diacritics)
• rejection of invalid scopes («10k words», multi-folder requests, etc.)
• language-specific grammar rules where needed

Tech stack:

• 100% native SwiftUI
• CloudKit sync
• OpenAI for example sentences (with strict quotas + rate limiting to avoid cost blowups)

Free tier: 4 folders, 50 cards each. Subscription unlocks everything with a 7-day trial. No ads, no tracking beyond crash + product analytics.

If anyone tries it, I’d genuinely appreciate feedback - especially on:

• AI sentence quality edge cases
• where the study flow feels unintuitive or too «manual»

Happy to share a promo code with anyone who wants to try it and give feedback.
App Store: https://itunes.apple.com/app/id6498724298