A method, comprising:receiving a first sequence of three-dimensional (3D) maps over time of at least a part of a hand of a user of a computerized system；segmenting the 3D maps in order to extract 3D coordinates of a first point located on a knuckle of the_finger on the hand and a second point at a tip of the finger；calculating a line segment that extends through the first point and the second point toward an area where one or more interactive items are presented by the computerized system；identifying a target point where the line segment intersects the area； andin response to a motion of the hand indicated by the 3D maps, engaging an interactive item presented in proximity to the target point.
