English: Four particles moving in a wave-like sinusoidal potential. There is no damping, so their speed at each location is a function of their current height. The slow green particle on the left and the faster blue particle on the right are each trapped in one of the potential wells, while the fast pink particle going left and the slower brown particle going right are free to pass over each hill. The domain is periodic, so a particle that exits right soon reappears from the left.