This script allows us to modify the springs that make up the edges of the bridge. Remember that the spring doesn't generate any force when the x in -kx is 0. x in this case is the delta from the spring at rest. That is what this computes. Here we changed the k value from -1400 which is a very stiff spring, to -400, which is quite a bit softer. Less force is generated from the same delta x. Note that the bridge is now sagging significantly more now.