YC startup
The founders dropped their own designs for mine, and their investor portal shipped in 4 days.
The founders had Figma designs. I redesigned the exchange in Claude, built it end to end, and they kept mine
- Company
- Y Combinator startup (name withheld)
- Product
- Exchange app
- Started from
- The founders' Figma designs
- Status
- Past work
Context
A Y Combinator-backed startup building an exchange where customers own fractions of vaulted assets. The first version is paper trading: every customer starts with $25,000 of play money to buy and sell.
The problem
There were Figma designs for the app, but they didn't feel like a trading product people would come back to. Another round of redrawing in Figma would have meant more mockups and still nothing anyone could actually use.
Real screens
Screens from the exchange app design I built.
What I built
Starting from the Figma designs and my own ideas, I prototyped a new design in Claude in about 30 minutes, as a working app the founders could click through, not a set of mockups.
The new design went straight into my app-builder pipeline: design system, app scaffold, tests and CI.
Buying and selling, indexes, individual asset pages, portfolio, a leaderboard, watchlists and search.
On their exchange API I built email-code sign-in with rotating sessions, the cash ledger with the $25,000 starting grant, fractional buys with a price preview, portfolio and order history, index list and detail, watchlists with launch alerts, and search across indexes and assets.
Separately, I built their SPV portal alone in four days (18 to 22 September 2026): public deal pages, investor sign-in and a staff admin area, with CI from day one.
Result
The founders dropped their own Figma designs and went with the prototype I built in Claude in 30 minutes, shipped through the pipeline as the full exchange app with its backend.
Stack
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