Knotty gestures: subtle traces to support interactive use of paper

We introduce the knotty gesture, a simple yet powerful technique for interacting with paper. Knots are tiny circles that can be added to any gesture. Users can leave subtle marks that permit both immediate interaction in the flow of writing and create rich opportunities for future interaction. We identify diverse applications of knotty gestures and explore alternative techniques for interacting with their traces. We conducted two experiments to evaluate the design and recognition heuristics and demonstrated that people can successfully execute knotty gestures, even without feedback. Knotty gestures provide users with a subtle, in-the-flow-of-writing technique for tagging information and subsequently interacting with the paper.