Mobile-First Breakpoint Cascade Simulator

Mobile-first design isn't just a design philosophy — it's a concrete CSS cascade strategy with measurable performance consequences. This simulator builds a real breakpoint stack from a viewport-width slider, a min-width (mobile-first) vs max-width (desktop-first) toggle, and a network profile, then computes exactly how many kilobytes of CSS are render-blocking and how long the first paint takes under the standard latency-plus-transfer model. A continuous stream of instanced data packets flows through the 3D breakpoint tower at a pace set by the bandwidth-delay product, making visible why a mobile-first, min-width stylesheet lets constrained mobile connections skip past CSS that can't even apply at their width — while a desktop-first, max-width bundle forces every device to download the whole thing before it can render anything.