/* ============================================================
   base.css — 重置、排版、可访问性、氛围层、降级动效
   ============================================================ */

*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  /* 锚点定位预留吸顶导航高度 */
  scroll-padding-top: calc(var(--header-h) + 16px);
}

body {
  background-color: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: var(--fs-400);
  line-height: 1.75;
  letter-spacing: 0.02em;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
  min-height: 100vh;
}

/* ---- 氛围层 1：LOGO 双色径向渐变网格 ---- */
.atmosphere {
  position: fixed;
  inset: 0;
  z-index: -2;
  pointer-events: none;
  background:
    radial-gradient(58rem 42rem at 10% -8%, rgba(124, 108, 255, 0.16), transparent 60%),
    radial-gradient(64rem 46rem at 96% 4%, rgba(255, 158, 44, 0.14), transparent 58%),
    radial-gradient(50rem 40rem at 50% 110%, rgba(124, 108, 255, 0.08), transparent 60%);
  filter: blur(0.5px);
}

/* ---- 氛围层 2：细网格线 ---- */
.gridlines {
  position: fixed;
  inset: 0;
  z-index: -2;
  pointer-events: none;
  background-image:
    linear-gradient(rgba(245, 241, 234, 0.028) 1px, transparent 1px),
    linear-gradient(90deg, rgba(245, 241, 234, 0.028) 1px, transparent 1px);
  background-size: 56px 56px;
  mask-image: radial-gradient(80rem 60rem at 50% 0%, rgba(0, 0, 0, 0.9), transparent 80%);
  -webkit-mask-image: radial-gradient(80rem 60rem at 50% 0%, rgba(0, 0, 0, 0.9), transparent 80%);
}

/* ---- 氛围层 3：SVG 噪点颗粒 ---- */
body::after {
  content: "";
  position: fixed;
  inset: 0;
  z-index: 3;
  pointer-events: none;
  opacity: 0.05;
  mix-blend-mode: overlay;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='.8' numOctaves='2'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
}

/* ---- 排版 ---- */
h1,
h2,
h3 {
  font-family: var(--font-display);
  font-weight: 900;
  line-height: 1.1;
  letter-spacing: -0.02em;
  color: var(--color-text);
}

p {
  max-width: 68ch;
}

a {
  color: inherit;
  text-decoration: none;
}

ul,
ol {
  list-style: none;
}

code {
  font-family: var(--font-mono);
  font-size: 0.92em;
  letter-spacing: 0;
  background: rgba(255, 158, 44, 0.1);
  border: 1px solid rgba(255, 158, 44, 0.22);
  border-radius: var(--radius-sm);
  padding: 0.1em 0.4em;
  color: var(--color-accent);
  font-variant-numeric: tabular-nums;
}

em {
  font-style: normal;
  /* 标题内强调：橙金渐变文字，呼应 ∞ 彩带暖端 */
  background: linear-gradient(100deg, var(--color-violet) 0%, #ffb02e 55%, var(--color-accent) 100%);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  color: transparent;
}

img,
svg {
  display: block;
  max-width: 100%;
}

/* ---- 可访问性：焦点可见 ---- */
:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}

/* ---- 跳转链接 ---- */
.skip-link {
  position: absolute;
  left: var(--space-3);
  top: -100px;
  z-index: 100;
  background: var(--color-accent);
  color: var(--color-accent-ink);
  font-weight: 700;
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-sm);
  transition: top var(--dur-fast) var(--ease-out);
}

.skip-link:focus {
  top: var(--space-3);
}

/* ---- 滚动浮现（由 main.js 的 IntersectionObserver 加 .in） ---- */
[data-reveal] {
  opacity: 0;
  transform: translateY(24px);
}

[data-reveal].in {
  opacity: 1;
  transform: none;
  transition:
    opacity var(--dur-base) var(--ease-out),
    transform var(--dur-base) var(--ease-out);
}

/* ---- Hero 一次编排入场：6 组错峰 80ms ---- */
@media (prefers-reduced-motion: no-preference) {
  .hero-step {
    opacity: 0;
    transform: translateY(28px);
    animation: hero-in var(--dur-slow) var(--ease-out) forwards;
    animation-delay: var(--d, 0ms);
  }

  @keyframes hero-in {
    to {
      opacity: 1;
      transform: none;
    }
  }
}

/* ---- 降级：用户偏好减少动效时全部关闭 ---- */
@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }

  [data-reveal] {
    opacity: 1;
    transform: none;
  }

  .hero-step {
    opacity: 1;
    transform: none;
    animation: none;
  }
}