Here is a real-time demo where I use #OpenSees to compute the 5%-damped elastic response spectrum for the Loma Prieta Saratoga-Aloha Ave record. The top charts show the input ground motions, on the left, and the displacement response of all the systems, on the right. In the bottom figure you can watch the actual models in 2D (the response is 1D only, horizontal), starting with the most flexible on the left and stiffer systems as you head right. You can see the SDOF systems with different periods respond differently to the same excitation. This video is part of a course I am developing for Silvia Mazzoni's Brainery @ courses.silviasbrainery.com