STRENGTHS enables interactive multitouch applications on everyday surfaces. uses the users hands, arms, and legs as graphical, interactive surfaces users can transiently appropriate surfaces from the environment to expand the interactive area eg books, walls, tables. uses all these surfaces without any calibration
WEAKNESS the system is sensitive to approach angle of fingers. require fingers to be outstretched to be recognisable. the system assumes that the user is a right hander projection distance limited classification driven approach suffers from scalability issues since it is not possible to build a classifier for every conceivable surface.