I like the concept. it's not clear that you have to use an offline editor though, I first thought you could do the mockup work in my browser. maybe I missed thi

I like the concept. it's not clear that you have to use an offline editor though, I first thought you could do the mockup work in my browser. maybe I missed this, but can you add notes to the mockups you put online, for example to guide a user through the design? I noticed an "Add note" feature in the screenshot of the editor, but it's not clear if those get copied to the online shared version.