Click the green < > Code button, switch to the Codespaces tab, and click your existing codespace to resume it. Do not create a new codespace every time, that will waste your free hours and leave you with unrelated environments.
Unused Codespaces get deleted after about a month of inactivity. This sounds scary but only affects the environment, not your files: everything you’ve committed and synced is permanently safe on github.com. If your Codespace disappears, just create a fresh one on the same repository, and all your source will reappear. The lesson: commit often.
