This project aims to create an element able to regulate light inside a room depending on the amount of sunlight hitting a window. It is a reactive light diffuser made of paper and white cardboard. The element is connected to an Arduino board that evaluates the amount of sunlight and translates it to movement.Due to the materials used in the project the element does not weight much , and it can easily be attached to the windows using magnets. This allows a temporary use of the element that is ideal for an exposition in the Haus am Horn.