:root {
  /* Apple 灰阶 */
  --color-bg: #ffffff;
  --color-bg-alt: #f5f5f7;
  --color-bg-dark: #000000;
  --color-surface-dark: #1d1d1f;
  --color-text: #1d1d1f;
  --color-text-secondary: #6e6e73;
  --color-text-on-dark: #f5f5f7;
  --color-text-secondary-on-dark: #86868b;
  --color-hairline: rgba(0, 0, 0, 0.1);
  --color-hairline-on-dark: rgba(255, 255, 255, 0.14);

  /* Apple 链接蓝 / 按钮蓝 */
  --color-accent: #0071e3;
  --color-accent-hover: #0077ed;
  --color-link-on-dark: #2997ff;

  /* Apple Intelligence 式渐变 */
  --gradient-hero: linear-gradient(108deg, #0894ff 4%, #c959dd 36%, #ff2e54 68%, #ff9004 96%);
  --gradient-soft: linear-gradient(108deg, #3a8dff, #a855f7 50%, #ff5e8a);

  /* 字体 */
  --font-stack: -apple-system, BlinkMacSystemFont, "SF Pro Display", "SF Pro Text",
    "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;

  --text-hero: clamp(2.75rem, 1.2rem + 6.5vw, 5.75rem);
  --text-headline: clamp(2rem, 1rem + 4vw, 3.5rem);
  --text-sub: clamp(1.125rem, 1rem + 0.6vw, 1.5rem);
  --text-body: clamp(1rem, 0.95rem + 0.25vw, 1.0625rem);
  --text-caption: 0.875rem;

  /* 节奏 */
  --space-section: clamp(5.5rem, 4rem + 7vw, 10rem);
  --space-headline-gap: clamp(2.5rem, 2rem + 3vw, 4.5rem);
  --container-narrow: 740px;
  --container-text: 980px;
  --container-wide: 1240px;

  /* 圆角与动效 */
  --radius-card: 28px;
  --radius-pill: 980px;
  --duration-reveal: 0.9s;
  --ease-out-expo: cubic-bezier(0.16, 1, 0.3, 1);

  --nav-height: 52px;
}