Congratulations! Glad to see more people attempting this type of thing. The demo content design is pretty nice. Some good things in Easel, but I have lots of problems with all the tiny little controls. Also it's an interesting decision to use a canvas element instead of the DOM. Without solving the overall page layout issue, this is a nice drawing tool like others have mentioned, and kudos to the technical and design…
It's very common that I iterate by doing very messy things, like say, breaking menus apart into two just to see how it will work. A DOM-based tool will probably have a nightmare with this, and even if it manages to account for this elegantly, I know from experience that having too many iterations that actually mess up the code can only be a bad thing.
I like Easel's approach. I want to paint a "picture," then build it with hand-made CSS. I don't want some tool being smart about my workflow. Easel exports just the right building blocks so I can implement by picture into a webpage the way I want to.