Your friend, who is actively involved in the physical laws of optics, is trying to figure out how to get the light from point A to point B while there are obstacles between the points which do not let the light to go through. It will require a laser light and a bunch of mirrors to make the light reflect in different angles. Adjust the mirrors so that the beam coming from the laser reaches the crystal ball. While the first levels are going to be just a warm up for you, the others are going to be really challenging. Have fun.