Ziggy: Very Interactive Trigonometry. In this paper we describe a highly interactive touch-based application to teach the basics of trigonometry to secondary school students. The application, called Ziggy, lets students “touch” and “push” triangles, dynamically modifying the shape and size, and observe the effect on the angles, sides and the trigonometric ratios. We describe the pedagogical rationale behind Ziggy, the user interface and provide details on the implementation. An early version of Ziggy has been tested in small-scale experiments in the classroom