Codex

I wanted a free browser mahjong game for friends, so I asked Codex to help build one. The project worked enough to publish, but mahjong exposed the real limit of AI coding: human understanding still matters.

OpenAI has brought Codex into the ChatGPT mobile app in preview. Here is how beginners can get a first real Codex win with HTML, JavaScript, Python, and a realistic PC plus phone workflow.

How to use Codex in 2026: a practical guide to the app, CLI, prompts, skills, AGENTS.md, and automations so it becomes part of your real daily workflow.