This 2D simulator draws a city skyline from the side: a row of buildings with different heights and construction quality, each modeled as its own mass-spring-damper oscillator with a real natural frequency derived from its story count. Trigger a quake at a chosen magnitude, shaking frequency and duration, and watch each building's sway amplify according to how close the shaking frequency sits to its own resonant frequency — taller buildings resonate with slow, low-frequency shaking while short buildings resonate with fast shaking. Raise the building-code-strength slider to add damping and drift capacity across the skyline, and watch which buildings survive a severe quake and which ones cross their collapse threshold and come down.