A solver for the Gray-Scott reaction-diffusion model. Reaction-diffusion (RD) models are mathematical formulations of some chemical and biological processes that are quite common in nature: several substances react with each other while they spread out over the space. The simulation of a RD system leads to patterns that are reminiscent of those seen in many natural places, such as the skin of a leopard or the surface of a brain coral. This experiment implements a solver of a specific class of RD systems: the Gray-Scott model. Here the reacting substance can be seen as living cells that need food to reproduce and have limited lifetime. The user can place living cells with mouse strokes, can change the colors and can set the parameters of the model (the feed and death rates). Some interesting parameter presets are available too. This experiment is also a nice example of emergent complexity, where a set of simple rules results in complex behavior.