How do you approach responsive design and choose breakpoints?

Responsive design adapts UI to different viewport sizes and input methods. **Approach:** - Start mobile-first with fluid layouts. - Use content-driven breakpoints (when layout breaks), not device-specific ones. - Prefer flexible units (`%`, `rem`, `vw`) and modern layout tools (Grid/Flex). - Test touch targets, typography, and images. **Interview tip:** mention accessibility (zoom) and performance (serve appropriately sized images).