It runs on BookPress — a native binary that serves WordPress sites, the real themes and the real wp-admin, at native speed. Your sandbox is yours alone, on its own subdomain, on one process shared with everyone else's.
Your site lives for 15 minutes from when you start it. No sign-up, no data kept.
Full wp-admin. Write posts, try the editor, click around. It is really WordPress.
The site is removed 15 minutes after you start it. Nothing you do is kept or indexed.
Every live sandbox is served by a single native binary — that is the whole point of the counter above.
Migrating a real site is one copy of the database and files — same schema, same URLs.