Previously
In Part 4: Birth of the Kagemusha System, I wrote about the decision to turn my personal tool into a product and the challenge of building automated setup.
The core product was ready. Next, it was time to build the infrastructure to sell it.
What You Need to Sell
Having a system means nothing if you can't sell it. At minimum, I needed the following:
Landing Page (LP)
A web page that communicates the product's value and drives purchases.
Payment System
A way to collect payments. Credit card processing.
Post-Purchase Automation
Payment complete → send email → setup instructions. All automated.
At a typical company, you'd hire a designer for the LP, an engineer for payments, and a marketer for emails.
I didn't have that kind of budget. I had to do it all myself (with AI).
Stripe Payments — Uncharted Territory
When it comes to online payments, Stripe is the go-to. I'd heard the name. But "API key," "Webhook," "subscription"… I had no idea what any of it meant.
Creating the payment link itself was indeed simple. The challenge was what came after.
"When a user makes a purchase, automatically send an email and guide them to the setup screen."
To automate this, I needed to use something called a Webhook. A Webhook is essentially a notification that says, "Hey, when something happens on Stripe, let my server know."
Building the Landing Page — With Zero Design Experience
Next up was the landing page. Naturally, I'd never designed one before.
What Claude Code produced was a fully responsive, animated, professional-looking landing page.
I couldn't write a single line of HTML or CSS, yet by simply saying things like "add more whitespace here" or "change the button color," the page transformed in real time.
The Post-Purchase Automation Flow
The most challenging part was the automated flow from purchase to setup.
User Clicks the Purchase Button on the LP
They're taken to Stripe's checkout page to enter their card details.
Payment Complete → Webhook Fires
Stripe automatically sends a "payment successful" notification.
Activation Email Sent Automatically
An email with a setup link arrives in the user's inbox.
User Clicks the Link
They authenticate with Google, and setup begins automatically.
Done
Within minutes of purchasing, the system is ready to use.
If even one gear in this flow was out of alignment, the whole thing would grind to a halt. The Webhook doesn't arrive, the email won't send, the setup throws an error mid-process… I tested it dozens of times, fixing issues one by one.
I Built It All by Myself
Looking back at everything I've done, even I can hardly believe it.
| Task | Normally Done By | How I Did It |
|---|---|---|
| Attendance management system | Backend engineer | Me + Claude Code |
| Automated setup | Infrastructure engineer | Me + Claude Code |
| Stripe payment integration | Payment specialist | Me + Claude Code |
| Landing page | Designer + front-end developer | Me + Claude Code |
| Automated email delivery | Marketing engineer | Me + Claude Code |
How much would it have cost to outsource all of this? $7,000? $14,000?
What I actually spent was just the monthly fee for Claude Code's Max plan.
Next Time
[Part 6] The Tech Stack — Hitting the limits of GAS and making the decision to migrate to Cloudflare Workers. It's a technical topic, but I'll explain "why we moved" in a way that anyone can understand.
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