Build a Customer Acquisition Cost Calculator with Claude Code

Build a Customer Acquisition Cost Calculator web app. People search for "customer acquisition cost calculator" about 350 times a month, plus related searches like "cac calculator", "customer acquisition cost", "marketing cost calculator". The goal is a tool that ranks for those searches and makes money.

What it should do:
Create a CAC calculator with marketing spend and customer acquisition inputs. Calculate CAC by channel, time period, and campaign. Include LTV comparison, payback period, and ROI analysis. Add channel performance comparison and optimization recommendations. Focus on getting basic CAC calculations working 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 HubSpot, Google Analytics, Mixpanel do it and make ours simpler and faster.
3. Make it rank. Use "customer acquisition cost calculator" 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: /cac-calculator-[industry], /customer-acquisition-[channel], /marketing-cost-[business-type].
4. Monetisation: Freemium: Basic calculations, $15/mo premium + multi-channel analysis. 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.