CSS‑in‑JS (Styled‑Components, Emotion)

Write CSS inside JavaScript, enabling props‑driven styling.

import styled from 'styled-components';
const Button = styled.button`
  background:${props => props.primary ? '#0066cc' : '#ccc'};
  color:#fff; padding:0.5rem 1rem;
`;

• Styles are scoped to the component.
• Supports theming via ThemeProvider.