task done bit

[amitu]

Imagine if in a document we can give some tasks, say this is a learning document, and we show instructions to the reader to do something, and then show a "Done" button when user has done that thing. And if we can remember this done bit for that user. It would be further cool if we can show some sort of progress, like if this is a book, and each document represents a chapter, and each chapter has a bunch of such done buttons, so reader can see their progress in the course, chapter by chapter, what percentage you have done each chapter.