I built this application as a fun way to help develop and understanding of the role of the foci in conics. It is a billiards-type game where the cushion is curved like a parabola, ellipse or hyperbola. Judging the angle of reflection from the curve is really quite difficult in isolation, but with knowledge of the properties of the particular conic, the solution is clear. Various applications of these reflective properties are briefly mentioned as well. If you like this activity, please follow me on Twitter and help me increase the visibility of this and the other activities at The Mathenaeum).
5 February 2016 Edit: 4 February 2016