Build a Caption Writer with Claude Code

Build a Caption Writer web app. People search for "caption writer" about 800 times a month, plus related searches like "social media caption generator", "instagram caption writer", "post caption ideas". The goal is a tool that ranks for those searches and makes money.

What it should do:
Build a caption writer web app. Create a homepage with post description input and platform selector (Instagram, Facebook, Twitter, LinkedIn). Add tone options (casual, professional, funny, inspirational) and length preferences. When users generate, show multiple caption variations with emoji suggestions and hashtag recommendations. Include engagement prediction scores and A/B testing options. Add save/export functionality and template library. Use social media-inspired design with platform-specific branding. Focus on caption generation and customization first.

How to build it:
1. Read this folder first. If it is empty, set up Next.js (App Router, TypeScript, Tailwind). Write a short PLAN.md with the pages, components, any library or API you need, and what you are leaving for later. Then build.
2. Put the tool itself on the homepage so a visitor can use it within seconds, with no sign-up. Do the processing in the browser where you can, so it is fast and cheap to run. Look at how Copy.ai, Jasper, Writesonic do it and make ours simpler and faster.
3. Make it rank. Use "caption writer" in the title tag, H1 and meta description. Under the tool, add a short how-to and an FAQ with FAQPage schema, and add a sitemap and robots.txt. Scaffold these programmatic pages from one template and a data file: /caption-writer-for-[platform], /[industry]-caption-generator, /write-captions-for-[content-type].
4. Monetisation: Freemium: 30 captions/month, $6/mo unlimited + templates. Add a pricing page and the free usage limit, and leave Stripe checkout as a clearly marked stub with the environment variables it needs.
5. Run it locally and test the main flow end to end, including edge cases like empty input and very large files. Fix what breaks, then finish with a summary of what works, what is stubbed and how to deploy it to Vercel.

Paste it into Claude Code in an empty folder. It plans first, so read PLAN.md and steer before it starts building.