If you take about optimizing then games are the prime example of doing that. You don't load textures every frame into gpu memory. Tou don't load vertices into memory every frame. Sure they repaint every pixel every frame. But low level your display driver is doing that anyway. The cpu cycles are not in sending the RGB value to each pixel. We are far beyond that bandwidth issue. Recalculating every single position in a css styled document is pretty heavy. There are millions of calculations done to solve flex boxes, floats, percentual widths etc. this example is doing something like that. Super heavy. Super inefficient. Super bad.