Looks really nice.

Can I get this on my desktop? (In other words: Can I work on this from a plane?)

I don't see anything about pricing in there, so using a web service (and having to log in...) to use this, I'm not super happy about. Balsamiq has a good system: They have both a desktop and a web version, let you import/export between the two, and charge you for licenses and online storage.

[edit: And furthermore, if you do a desktop version, you can also do it as a vscode extension, that'd be super cool]