Ball bouncing in a cube
Movement of a ball inside a cube. Don't miss the gravity effect. Also, it is easy to observe the parabola the circular projection on the vertical faces move in. A good simulation to understand 3-dimensional motion, with uniform speed along the horizontal directions, and acceleration due to gravity along the vertical direction. It also provides the simulation of reflection along the surfaces of the cube. This can be extended to create games using GeoGebra