patrickz
Before you start
Do this first: Get started with ChatGPT and Codex: a first harmless task (25 min)
A computer, a coding agent such as Codex, and an empty practice folder. Git (version control) lets you save checkpoints you can return to; if you have never used it, ask the agent to set it up in this folder and explain each command.
Why this lesson exists
Patrick’s rough answer to what it takes to build something useful at home was about twenty dollars, plus a willingness to read error messages without taking them personally. Subscription prices change; the durable lesson is a narrow problem, readable files and a tested complete loop.
The idea this guide practices: Build an app with an AI agent, one proven slice at a time. Prefer a story? Read the comic The Scope Creep Mecha Is My Fault.
Do the exercise
Specify one job
Choose a reading list with add, complete and remove actions. Define what happens after a page reload. Use fictional data and keep sign-in and payments out of the first version.
Ask for a plan grounded in files
Open the practice folder in your coding agent. Ask for the simplest implementation and an explanation of each file. Approve a small scope before code grows.
Build and run locally
Ask the agent to implement the loop, explain the run command and open a preview. Use the interface yourself. An error-free build is only one check.
Test the unhappy paths
Try an empty item, a long title, a reload and a small phone viewport. Record results and fix one failure at a time. When a fix works, ask the agent to commit it with a short message describing the fix, so you can return to this point.
A prompt to adapt
Copy it and paste it as-is into your assistant.
In this practice folder, build a simple reading list with add, complete and remove actions and local persistence. First inspect the folder and explain the smallest file structure. Use fictional data, no accounts or paid APIs. Run it, test empty input and reload behavior, and show me the preview and remaining limits.
What this looks like
The app is not finished because a screenshot looks good. Add a book, reload, complete it, reload again, then remove it. Those five actions prove the basic loop.
Check your result
Use evidence from your output. A confident explanation from the AI is not enough.
If it isn’t working
If the agent proposes a database and authentication immediately, restate the local-only milestone. If preview fails, paste the exact error and ask for the smallest diagnosis first.
Optional. Progress stays in this browser.
Where this came from
Adapted from the archived LinkedIn theme “The Twenty-Dollar Software Company.” See the post coverage and editorial method. Original LinkedIn post ↗
Prepared September 2026. Tools and interfaces change; use current official setup instructions. Session lengths are estimates.