Advanced CSS Topics: Transitions, Responsiveness, and Variables

Describe the difference between CSS transitions and keyframe animations and their use cases.

Implement performant animations by primarily using the 'transform' and 'opacity' properties to avoid triggering layout or paint.

Explain the 'mobile-first' responsive design philosophy and how min-width media queries facilitate it.

Describe the purpose of CSS custom properties (variables), their scoping rules, and their advantages over preprocessor variables.