Looking Glass is a geometric optics construction set that allows students to create and explore situations involving several objects, lenses, mirrors and images. This software takes an interactive, visual approach to physics. Looking Glass will help students develop an intuition for the effect of lenses and mirrors on light rays. Students will gain a better understanding of the physics behind the images. By creating and exploring their own lenses and mirrors with Looking Glass, students encounter many of the core concepts in optics. Looking Glass was designed for use in high school and college physics studies. The software offers convex and concave lenses and mirrors; virtual and real images; thin-lens modeling; and mks units. Online help and tutorials are provided to help teachers integrate the software into their curriculum. With Looking Glass, students can now explore the behavior of lenses and mirrors using only their computer, Living Graph Paper and their imagination.