This simulation allows you to set the natural length, L, and spring constant, k, of an ideal (massless) spring, to load it with a mass, m, and then set it oscillating with some amplitude, A.
When you click "Go" a strip chart is drawn marking out the vertical position of the lower end of the loaded spring. Clicking "Reset" not only stops the motion and clears the strip chart trace but sets the spring at its equilibrium position.