This tool might be good for static web pages where the copy and layout is the most important thing, and perhaps basic web apps of the kind that Rails generates with scaffolding. But it doesn’t seem suited for most web apps. The library is missing components needed to represent many things. For instance, you can’t represent images. You can’t represent most things that would be a “custom view” of data – tables, graphs, diagrams, draggable components, etc..<p>I tried mocking up Napkin itself in Napkin and ran into trouble. The sidebar needs components of all types (Article, Form, and Navigation), so I need to split it into multiple boxes. But I can’t arrange the app by columns, only by rows, so the main content is vertically aligned with boxes in the sidebar, though it shouldn’t be. I couldn’t represent the screen prototype view – there’s no way to draw “dotted boxes”. I also tried mocking up another note-database app, and that went better – I typed bullets at the beginning of Article paragraphs to represent my bulleted list of notes.<p>At least the app is very polished. I enjoy the simplicity of the model – the grid-based layout and the organized types of content. The site also looks clean and pretty. Though a few interactions are weird, such as how you need to drag components from the sidebar to add them, but you can only click a “+” button to add elements listed in the sidebar.<p>A small bug: if you have a 3-column row and put content in columns 1 and 3, then Share Screen to preview, column 3 moves to the left to take empty column 2’s place. I would prefer it to stay on the right side.