Building Ultra-Responsive Design Systems with Next.js 15 & Tailwind CSS

## Architecture of a High-Velocity Design System When scaling web applications across web and mobile viewports, having a unified token system eliminates styling inconsistencies and dramatically cuts engineering overhead. ### 1. Token Hierarchy Organize tokens into base primitives (colors, spacing), semantic aliases (`bg-surface-elevated`), and component overrides. ### 2. Micro-Animations & Fluid Layouts Leverage CSS container queries and sub-100ms cubic bezier transitions to create interfaces that feel tactile and responsive. ### 3. Accessible Focus Rings Ensure keyboard navigation meets WCAG 2.2 standards with visible, contrasting focus states across all interactive controls.