:root {
  /* Colors from DESIGN.md & 设计参考.html */
  --color-signal: #C62828;      /* Shormar Red: Primary action, accents, max 5% */
  --color-dark: #252C31;        /* Gunmetal: Main headings, dark panels, navigation */
  --color-gunmetal: #252C31;
  --color-steel: #69737B;       /* Steel Gray: Secondary text, borders, specs */
  --color-concrete: #EEF1F2;    /* Concrete: Light partitions, card backgrounds */
  --color-white: #FFFFFF;       /* Pure White: Background, contrast text */

  /* Borders & Lines */
  --line-light: rgba(37, 44, 49, 0.12);
  --line-medium: rgba(37, 44, 49, 0.2);
  --line-dark: rgba(255, 255, 255, 0.14);
  --line-dark-soft: rgba(255, 255, 255, 0.08);

  /* Typography */
  --font-display: "Barlow Condensed", "Arial Narrow", -apple-system, BlinkMacSystemFont, sans-serif;
  --font-body: Inter, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;

  /* Typography scale */
  --text-display: clamp(3.2rem, 7.5vw, 6.4rem);
  --text-h1: clamp(2.4rem, 5vw, 4.4rem);
  --text-h2: clamp(1.85rem, 3.2vw, 3rem);
  --text-h3: clamp(1.35rem, 2vw, 1.85rem);
  --text-h4: 1.15rem;
  --text-body-lg: 1.125rem;
  --text-body: 1rem;
  --text-small: 0.8125rem;
  --text-micro: 0.6875rem;

  /* Layout & Spacing */
  --max-width: 1280px;
  --content-max: 820px;
  --gutter: 24px;
  --radius-sm: 2px;
  --radius-md: 4px;

  /* Animation & Transitions */
  --transition-fast: 180ms ease;
}