This painting machine responds to light levels -- creating red splatters when the light is brighter, and yellow when the light is not so bright. The mechanism is designed to "whap" the screen to knock the paint onto the paper. If it is bright, the motor will hit one side of the screen, and when the light dims (the sun goes behind a cloud) it will reverse direction, go a bit further, then continue "whapping" the screen on the other side. Here's a view of the light-sensitive painting machine, designed to be used outside. Another view of the mechanism. Metal weights on strings tied to a dowel knock the paint onto the paper. Painting made by the summer sun painter.