I really like the concept, which suits the theme very well! The sound and visuals are also well done.
My biggest problem is with the purple crystals. The first levels are very easily understandable and easy, maybe a bit too easy, but the player is able to plan the reaction perfectly. At least to me, the crystals are very unpredictable in terms of how they are going to influence the beam of light. This makes the later puzzles come down to trial and error instead of careful planning.
Either way it's a pretty enjoyable game, but the last levels feel too clutterd.