Your progress
There’s no account: progress lives in this browser. To use another phone or computer, take it with you here, and bring it back the same way. Merging only ever adds.
on this browser
Nothing yet. Progress is saved in this browser as you go: start with the first lesson.
take it to another device
A link is easiest: send it to yourself and open it on the phone or laptop you want the progress on. The progress travels after the #, the part of a link browsers never send to a server.
bring it here
use it offline
Every page you open is kept on this device, so it opens again without a connection. To take the whole course on a plane, save it all at once (or add the site to your home screen on a phone).