That's definitely closer to what I'm talking about. After trying that link, I think my suggestion is a little different. I should be able to "Swap it" without an account, because for a brand new user, the app's goal should be to let me build something that's novel enough that I want to save it (beyond my browser's session cookie).
When I see "Unsaved" in the UI and I care enough about it to click "Save," the app has done its job -- and it's the perfect time to ask for my email address :)