Cross-Platform Gaming Ecommerce App

I need a single code-base mobile application that runs smoothly on both iOS and Android. The concept blends a lightweight casual game with an in-app shop, so users can play, earn or collect items, then purchase digital or physical goods without leaving the app.

Core requirements
• Dual-platform release built with a framework you are comfortable with (Flutter, React Native, Unity + native bridges, etc.).
• Two key modules:
 1. Gaming loop (simple, replayable, low-latency).
 2. Ecommerce flow (catalogue, cart, checkout, order history).
• Authentication must support email + password, social media login and mobile number with OTP.
• Clean, well-documented code and API hooks so I can plug in payment, analytics and push notifications later.

Deliverables & acceptance
1. Signed APK / IPA (TestFlight build) ready for QA.
2. Full source code in a private Git repo with commit history.
3. Setup notes for app store submission and environment variables.
4. A short video walkthrough proving all auth methods, a complete purchase and a full game round.

I will provide brand assets, game art and product data; you handle the architecture, UI, and integration. Tell me which tech stack you prefer, a rough milestone plan and any prior work that shows similar cross-platform experience.