Why this course exists
Everyone has a half-finished personal website in their head: an about page, the things you've built, the ideas you keep meaning to write down. This course gets it out of your head and onto the internet - built from scratch WITH Codex, OpenAI's coding agent, on nothing more than a personal ChatGPT Plus subscription. Six sessions, one real shipped website, and a working command of the tool by the end.
What Codex actually is 6 min live
Codex is an agent: you give it a goal, it gathers context, takes action in your files, and produces something real - code written, tests run, changes reviewed. One agent, five doors to reach it.
LiveAn agent, not an autocomplete3 min▶
Codex is not a chat window that emits code snippets. It works like a junior engineer with a terminal: it reads your files, plans, writes code, RUNS it, reads the errors, fixes them, and shows you the result - looping until the goal is met or it needs your call. You review and steer; it does the labor.
- It sees your project: point it at a folder and it explores the real files - no copy-pasting code into a chat box.
- It acts under your permissions: what it may read, write, and execute is a setting you control (Part 2), not a hope.
- It verifies: the habit that separates agents from autocomplete - it can run the thing it just built and check.
The moment it clicks for most people: you type "the contact link is broken on mobile" - and instead of an explanation, Codex opens the file, finds the overlapping element, fixes the CSS, and shows you a diff. Ten seconds. That gap between "telling you about code" and "doing the work" is the entire product.
LiveWhich door when - the five surfaces2 min▶
| Surface | Reach for it when | In this course |
|---|---|---|
| Codex CLI (terminal) | Building in a local folder - full control, fastest loop | Sessions 1-5, home base |
| Desktop app (Codex mode) | Same power, friendlier face - great if terminals feel hostile | Valid alternative throughout |
| IDE extension | You live in VS Code and want Codex beside the editor | Optional, Session 2 note |
| Codex cloud | Delegate a task and close the laptop; run tasks in parallel | Session 6 |
| Code review | Check changes before they ship - /review locally, @codex on GitHub PRs | Session 5 |
Self-studyModels, credits, and what Plus actually gets you3 min read▶
Codex is included in every ChatGPT plan - Free through Enterprise. On Plus ($20/month), usage is metered in 5-hour windows, and cloud tasks and code reviews share the same pool:
| Model | Character | Plus: messages per 5-hr window |
|---|---|---|
| GPT-5.6 Sol | Deepest reasoning - hard problems, gnarly bugs | ~15-90 |
| GPT-5.6 Terra | The balanced default - most work happens here | ~20-110 |
| GPT-5.6 Luna | Fast and light - quick edits, questions | ~50-280 |
| GPT-5.4 mini | Bulk simple tasks | ~60-350 |
- Switch anytime with
/model- model plus reasoning effort per task. - The budget habit: default to Terra; reach for Sol when genuinely stuck; drop to Luna for small edits. Ranges are wide because message cost scales with how much thinking a task needs.
- Hit the ceiling? Plus users can buy extra credits, or simply wait for the window to reset. For this course's website project, Plus limits are comfortable - a session's build fits well inside one window.
Setup on your Plus plan 5 min live
Two minutes of installing, one sign-in, one decision about permissions. That's the whole barrier to entry.
LiveInstall and sign in2 min · then Demo 1▶
Signing in with ChatGPT links Codex to your Plus plan - no API key, no billing setup, nothing else to configure. The desktop app route is even shorter: install the ChatGPT app, open a folder, pick Codex mode.
LivePermissions - the safety dial2 min▶
Codex acts under a permission gate you control with /permissions: from read-only (it can look, not touch) through auto-edit in the project folder, up to running commands with approval. Two rules carry you through this whole course:
- Start where you're comfortable. Read-only on day one is a fine choice - promote it as trust builds. Approval prompts are a feature: every "may I run this?" is a chance to learn what it's doing.
- The sandbox is real: Codex works inside your project folder's boundary; it asks before going beyond. Your website project is a perfect training ground - nothing in it can hurt anything.
Self-studyThe other doors: desktop app modes and the IDE extension2 min read▶
- Desktop app has three modes: Quick Chat (casual questions), Work (research, documents, analysis), and Codex (software work on a folder). Same account, same limits - mode just sets the working style.
- IDE extension: Codex inside VS Code, seeing your open editor context. Same agent; useful once you're editing the site by hand alongside it (Session 4 territory).
- Session continuity:
codex resumepicks up a previous conversation in the CLI - your project's context survives lunch. - Everything shares your setup: the AGENTS.md and skills you'll build in Session 3 apply across CLI, app, and IDE automatically.
Talking to Codex: the GCOB structure 4 min live
OpenAI's own guidance boils down to four elements. No syntax, no magic words - just four questions answered in plain language, then iteration.
LiveGCOB in action, plus the Codex-specific habits4 min▶
Three Codex-specific habits from the official guide, worth tattooing somewhere:
- Bugs get reproduction steps: "the menu breaks when I resize below 400px" beats "menu is broken".
- Name your constraints: "minimal changes", "don't touch the design", "keep it readable for a beginner" - boundaries prevent enthusiastic rewrites.
- Ask for verification: end big asks with "then check it works and tell me how you verified". Agents that verify are agents you can trust.
A first-timer's actual session: her first prompt was "make my website" - she got a generic template and hated it. Rewritten with GCOB (real goal, her taste in context, plain-code boundary), the second attempt was recognizably HERS. Same tool, same evening - the four questions were the difference.
One website, six sessions 3 min live
Every session advances the same build. No toy exercises - by Session 5 this is live on the internet with your name on it.
Install, sign in, first conversation ★ 8 min · everyone installs
Run the installer (Part 2 box) - or install the ChatGPT desktop app if you're going the no-terminal route.
Make the project folder: mkdir my-site && cd my-site - then run codex and sign in with your ChatGPT account.
First conversation, no stakes: "Introduce yourself - what can you do in this empty folder, and what do you need from me to be useful?" Read the answer; it's a better feature tour than any slide.
Run /status - see your model, permissions, and folder. Then /model - look at the options, leave it on the default (Terra).
Plan YOUR site with GCOB ★ 10 min · everyone plans
Two quiet minutes with pen and paper: what are your three sections? (Default: about / things I've built / ideas I'm chewing on. Rename them to sound like you.)
Write your first real GCOB prompt - use the Part 3 example as a skeleton, but the Goal and Context are yours. Ask for a PLAN, not code yet.
Run it: "...Output: write SITE_PLAN.md in this folder - sections, pages, what each contains, and the build order you'd suggest. Boundaries: plan only, no code yet, keep it under a page."
Discernment lap: read SITE_PLAN.md, disagree with one thing out loud, and tell Codex to revise it. The plan is yours, not its.
Approve the plan. That file is Session 2's starting gun.
The revision moment is where ownership happens: "swap the blog for a shorter 'ideas' section - I'll write 200-word notes, not essays" turned a generic plan into one a real person would actually maintain. Codex is a great planner and a better listener.
Feel the permission gate ★ 4 min · follow along
Ask Codex: "Create a README.md that describes this project in two sentences." Watch the approval prompt appear (unless you've already granted write access).
Before approving, ask: "What exactly will you write and where?" - see it explain itself. THEN approve.
Open /permissions and set the level you're comfortable keeping for this project. There's no wrong answer - only your answer.
This week ◐ 30 min total
- Finish your SITE_PLAN.md if the session ran short - it gates Session 2.
- Have three GCOB conversations with Codex about anything ("Goal: understand what's in my Downloads folder..."). The structure has to become reflex.
- Gather your raw material: a short bio, 3-5 things you've built or shipped (a line each), 2-3 ideas you'd write about. Plain text in a notes file - Session 4 turns it into pages.
- Optional: watch OpenAI Academy's "Codex for Beginners" video - this session covered its content, but seeing the live-drive texture helps.
Three questions before you go 🎯 ◐ 90 seconds
1 · What makes Codex different from a chat window that writes code snippets?
Agent, not autocomplete: the gap between "telling you about code" and "doing the work" is the whole product.
2 · The GCOB elements are...
Four plain-language questions from OpenAI's own guide - then iterate in follow-ups. Results over steps, always.
3 · Codex asks to run a command you don't recognize. Best move?
The approval prompt is a feature and a free terminal lesson. Understand, then decide - trust is built, not granted.
Official sources covered
This session teaches the working content of OpenAI's official onboarding materials - docs at learn.chatgpt.com and free courses at OpenAI Academy.