Practical web and app services anyone can build with vibe coding

CODEX · VIBE CODING · WEB & APP

The first screen you made with AI,
turn it into a service people actually use.

A practical project where customers make reservations and administrators manage operations.
Build it with Codex, test it yourself, and expand from a web service to an Android app.

Take on the challenge of earning ad revenue and monthly subscription revenue with a service you built.
Aim for AdSense ad revenue with a free public service, or
offer repeatedly needed features as a SaaS and charge a monthly subscription fee.
Build, launch, and improve it yourself while developing the skills to achieve that goal.

💭 If a demo you built on your own went well but you started running into roadblocks as you added more features

You can quickly build an introduction page or a simple calculator with AI. However, when members, data, reservations, and admin features are connected, problems arise that cannot be identified from the interface alone.

• The login works, but will the information be properly protected? Even if my reservations are displayed correctly, accessing them through another account could reveal someone else’s reservations.

• The reservation button works, but who will get the last spot? It may work normally when you click it alone, but if two people apply at the same time or an administrator approves an application, the capacity may be exceeded.

You need to anticipate and verify situations like this to turn a demo I ran on my own into a service that other people can use.

⚠️ If you keep repeating “just get rid of the errors,”
you may run into even more obstacles after the fix.

If you accept AI’s fixes without criteria for checking the results, the visible symptoms may disappear while the underlying cause remains. For example, situations like the following may arise.

• What if you removed access restrictions to eliminate a retrieval error? The data may become visible again, but it could also expose other people's information. You need to check both the functionality and the permissions.

• What if you only disabled the button to prevent duplicate bookings? Duplicate bookings may still occur in another window or through repeated requests. Processing rules beyond the screen are also necessary.

You need to distinguish failed requests from the parts that worked and know what to check after making changes to break free from repetition.

🛠️ Learn developers’ design and validation, and
you’ll have a clearer idea of what to delegate to AI.

• Before building, define the relationships and rules first. Map out the user flows for customers and administrators, and connect the member, class, session, and reservation data. Document rules such as permissions, reservation statuses, and capacity in the MD planning document and acceptance criteria.

• After building it, verify even the situations where it could fail. Test with conditions such as different accounts, duplicate requests, and the last available spot. Use automated tests and build and type checks, and revert incorrect changes by reviewing the records.

In this course, we repeat these two processes from planning through implementation, revision, and deployment. It’s the process of establishing criteria for my own verification after the AI says, “It’s complete.”

🧭 Simply listening to a good explanation is not enough to complete
your service.

• If you only follow the example exactly, you’ll get stuck when the requirements change. To adapt the reservation structure to your business, you need to determine what needs to change not only in the interface, but also in the data and permissions.

• Even if you understand the theory, you may get stuck at launch without deployment experience. You need to experience everything from checking login and environment settings at a real URL to finding errors and rolling back updates.

So you’ll build one complete booking service from start to finish, culminating in a graduation project where you personally implement and validate your own requirements beyond the scope of the course.

🚀 Connect 20 years of web and app development experience to
your first service

Tani, who has 20 years of web and app development experience, guides you through the practical process of planning, building small, testing, and launching. We cover not only the moments when code is created, but also what to request and which results to verify.

The finished product will be an offline class reservation service. Experience the entire flow, from customer applications to administrator approval, web deployment, and app expansion, and learn development methods you can apply to your next ideas.

This is a conceptual example of a deliverable that extends from the web to an Android app as a single service.

📌 Features of This Course

• Connect a service from start to finish. Starting with an introduction screen, you will expand it to include member, reservation, and administrator features, deployment and operations, and even an Android app.

• Develop work habits for using Codex. Communicate the goals, scope, and completion criteria, then continue development with project work rules and work logs.

• We cover both expected behavior and behavior that must be prevented. We verify data access permissions, capacity limits, and duplicate requests starting from the implementation stage.

• You will also practice the process of fixing failures. You will locate errors, revert incorrect fixes, and verify your skills through assignments that involve repairing intentionally broken features.

Recommended for those who

If there’s something you want to build but you’ve found it difficult to connect the steps that come next on your own, let’s get started together.

🎯 After completing the course

• You will experience the process of organizing an idea into an MD planning document that includes screens, data, permissions, and completion criteria.

• You will build a reservation web service that connects customer sign-up, booking, and cancellation with the administrator’s class management, approval, and rejection.

• Verify permissions using different accounts and invalid requests, and practice automated testing and troubleshooting.

• Use GitHub and Vercel to publish the web service, covering the basics of operations, including environment configuration, error logging, backups, and rollbacks.

• Extend the same project into an Android app and prepare a test deployment.

• In the graduation project, you will implement and validate one of your own requirements.

🛠️ What you’ll learn

Develop an offline class reservation service in four stages. Payments are covered as a practical extension in a test environment, while iOS is treated as an optional step.

The GIF below is a conceptual animation explaining the learning flow.

👨‍💻 The person who created this course

Hello! 👋
I’m Tani, a developer who talks about one-person businesses built with AI.

20 years of experience in web and app development, and 13 years working as a freelance developer.
I have worked on the design and development of projects for major companies such as Samsung Electronics and LG.

I’m currently researching and sharing how to use AI to build websites and apps yourself and develop them into services used by real users. On YouTube, I share my development process along with my journey of exploring AdSense, content monetization, and one-person businesses.

In this course, based on hands-on experience, we will guide you through the process of deciding what to build, asking AI for assistance, reviewing the results, and improving the service you have launched. Together, we will build a foundation in development that enables you to implement your ideas yourself and take on the challenge of monetization.

💼 Experience

• 20 years of web and app development experience

• 13 years of experience as a freelance developer

• Experience designing and developing projects for major corporations such as Samsung Electronics and LG

• Experience planning, designing, and developing corporate IT systems

🎥 YouTube · One-person businesses created with AI

I share my experience creating websites and apps with AI, vibe coding, AdSense, and content monetization.
Check out the channel first to see the explanation style you’ll encounter in the course and the actual creation process.

▶ Visit Tani's YouTube channel

📋 Notes Before Enrolling

Please review the practice environment, additional costs, and the scope of the optional components before getting started.