Interfaces for conceptual and creative design should recognize and interpret drawings. They should also capture users' intended ambiguity, vagueness, and imprecision and convey these qualities visually and through interactive behavior. Freehand drawing can provide this information and it is a natural input mode for design. We describe a pen-based interface that acquires information about ambiguity and precision from freehand input, represents it internally, and
echoes it to users visually and through constraint based edit behavior.

Electronic Cocktail Napkin