CSS3

CSS3 introduced modular specifications for modern web styling, including Flexbox, Grid, and hardware-accelerated animations.

CSS3 evolved the styling layer of the web by breaking the monolithic CSS 2.1 specification into independent modules. This shift enabled rapid deployment of transformative features like the Flexible Box Layout (Flexbox), CSS Grid, and media queries for responsive design. Developers leverage CSS3 to handle complex visual tasks (gradients, rounded corners, and drop shadows) directly in the browser, reducing reliance on image assets and improving performance via GPU-bound transitions and transforms.

https://developer.mozilla.org/en-US/docs/Web/CSS