TIM can simulate "impossible" optical components, for example windows that rotate the light-ray direction through 90 degrees around the window normal. We call such components METATOYs. TIM is an acronym for "The Interactive METATOY".
TIM has other features, at least one of them unique. These include the abilities
to simulate a camera that can focus on arbitrary surfaces, not just planes;
to visualisation of light-ray trajectories through optical systems;
to simulate the effect of light-ray "teleportation";