Inspiration
Scrolling through Instagram and now Threads, we kept seeing great ideas trapped in sloppy swipe-carousels. Designers spend hours in Figma; non-designers give up entirely. We wondered: what if AI wrote the copy, laid out the slides - all inside one mobile app? Cardsy was born to turn raw ideas into polished, swipe-ready stories in under five minutes.
What it does
Cardsy listens to a voice note or text prompt, distills the key message with an LLM, then auto-generates a multi-slide carousel in 30+ languages. Users tweak fonts, brand colors, and imagery; HD exports land straight in their Photos. The core app is free, while Pro features - premium templates, brand kits, Batch Export, and analytics- unlock via a RevenueCat subscription paywall.
How we built it • Frontend: SwiftUI with custom CarouselStack geometry for 3-D “peek” parallax. • AI pipeline: Gemini for summarization → Markdown → our Markdown-to-Slide parser • Paywall: RevenueCat SDK, using the new Paywalls API for remote A/B tests. • Storage: CloudKit for user drafts. • CI/CD: GitHub Actions + Xcode Cloud; TestFlight auto-deploy on every main push.
Challenges we ran into • Balancing GPT token usage with Shipaton’s free credits. • Synching CloudKit drafts across devices while maintaining offline editing. • Designing a paywall that converts without blocking creativity—iterated four times using RevenueCat’s experiment dashboard. • Threads still lacks a formal sharing API, so we had to reverse-engineer a share-sheet workflow.
Accomplishments that we’re proud of • MVP shipped in 36 hours with a 92 % crash-free rate. • Live A/B test hit a 14 % uplift in subscription starts by swapping “Unlock HD Export” for “Remove Watermark.” • Localization engine auto-translates carousels into right-to-left languages—first of its kind among carousel makers.
What we learned
Monetization is a product feature, not an afterthought; having RevenueCat from day one let us iterate on price and copy instead of wrestling with StoreKit. We also discovered that users value speed to first post over granular design control—hence the heavy lift from AI.
What’s next for Cardsy – Carousel for Threads, Instagram, TikTok • Threads deep-linking once Meta opens the API. • Auto-Reformat: one tap to convert a 1080×1080 carousel into Reels or TikTok sequences. • Template marketplace so designers can sell slide packs (RevenueCat’s new Marketplace entitlements look perfect). • Launch on macOS
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