Focused rays of ultraviolet light paint temporary landscapes on a layer of phosphorous dust. Operating on concepts of erosion and mutation, the installation changes its behaviour and visual appearance during the exhibition period: Each trace of light leaves a mark on a virtual mountain range, like water slowly washing out deep canyons. At the hidden digital core of the installation, a piece of code represents that imaginary landscape. Every beam of light projected onto it behaves like a drop of water, finding its way down to the valley. Whilst doing so, it slightly changes the mountain's shape, resulting in different trajectories throughout the passing of time. The evolution during the exhibition period is unpredictable, yet driven by simple universal laws, which once defined, remain untouched. The visual complexity of the work is created by repeated calculations of relatively simple mathematical functions. Phosphor is inspired by Benoît Mandelbrot's fractal geometry, early algorithmic art and contemporary big data models. The software and the mathematical processes have been developed by the artist.