A system design pass for TalkLooper, a spoken English practice app: why the first MCP version was elegant, why transcript-only analysis broke down, and how I would redesign the loop around raw audio, consent, speech events, and practice feedback.

A mobile design pass for Prism: local-first play, daily seeds, Supabase leaderboards, cloud sync, streaks, notifications, and reliability tradeoffs.

A PayPal-style wallet from a mobile point of view: payment intents, ledgers, risk checks, idempotency, webhooks, local state, and recovery flows.

A Robinhood-style trading app from quotes and orders to fills, buying power, ledgers, compliance, and trust on mobile.

Notes on how I think about mobile systems, product behavior, and high-level architecture.

The app-side version of the Slack design: state ownership, local storage, outbox, sync, navigation, accessibility, and reliable UX states.

Slack-style messaging through the mobile parts that get messy: offline sync, push notifications, local cache, read state, and failure handling.