/* ==========================================================================
   base.css — 重置、氛围层、排版基础、可访问性
   ========================================================================== */

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

* { margin: 0; padding: 0; }

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: var(--nav-h);
}

body {
  min-height: 100dvh;
  background: var(--c-bg);
  color: var(--c-text);
  font-family: var(--f-body);
  font-size: var(--fs-body);
  font-weight: 400;
  line-height: var(--lh-body);
  letter-spacing: var(--ls-body);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

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

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

button, input, textarea { font: inherit; color: inherit; background: none; border: 0; }

ul, ol { list-style: none; }

::selection { background: var(--c-accent); color: var(--c-void); }

/* ---------- 焦点：2px + 2px 偏移，暗底上用暖白 ---------- */
:focus-visible {
  outline: 2px solid var(--c-accent);
  outline-offset: 3px;
  border-radius: var(--r-xs);
}

/* ---------- 氛围层：渐变网格 + 细网格地平线 + 颗粒 ---------- */
/* 三层都固定铺满、不可交互，避免参与布局与命中测试 */
.atmos { position: fixed; inset: 0; pointer-events: none; z-index: var(--z-bg); }

.atmos::before {
  content: "";
  position: absolute; inset: -20%;
  background:
    radial-gradient(48rem 34rem at 8% -6%,  rgba(0, 225, 255, .22), transparent 62%),
    radial-gradient(42rem 32rem at 96% 4%,  var(--c-glow-cool),     transparent 58%),
    radial-gradient(52rem 40rem at 60% 108%, rgba(0, 225, 255, .10), transparent 60%);
  filter: blur(6px);
}

/* 细网格：1px 发丝线，用遮罩从中心向边缘消隐 */
.atmos::after {
  content: "";
  position: absolute; inset: 0;
  background-image:
    linear-gradient(to right,  rgba(242,239,233,.045) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(242,239,233,.045) 1px, transparent 1px);
  background-size: 88px 88px;
  mask-image: radial-gradient(120% 90% at 50% 0%, #000 20%, transparent 78%);
  -webkit-mask-image: radial-gradient(120% 90% at 50% 0%, #000 20%, transparent 78%);
}

/* 颗粒：SVG feTurbulence，5% 透明度叠加 */
.grain {
  position: fixed; inset: 0; z-index: 2;
  pointer-events: none; opacity: .05;
  mix-blend-mode: overlay;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='200' height='200'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='.85' numOctaves='3'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
}

/* ---------- 版心 ---------- */
.container {
  width: 100%;
  max-width: var(--maxw);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

main { position: relative; z-index: var(--z-content); }

section { position: relative; }

/* ---------- 排版基础 ---------- */
h1, h2, h3, h4 {
  font-family: var(--f-display);
  font-weight: 800;
  line-height: var(--lh-snug);
  letter-spacing: var(--ls-display);
  text-wrap: balance;
}

p { text-wrap: pretty; }

/* 等宽小标签：全站统一的"仪器刻度"语汇 */
.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: var(--s-3);
  font-family: var(--f-mono);
  font-size: var(--fs-label);
  font-weight: 500;
  letter-spacing: var(--ls-label);
  text-transform: uppercase;
  color: var(--c-muted);
}

.eyebrow::before {
  content: "";
  width: 22px; height: 1px;
  background: var(--c-accent);
}

.eyebrow--plain::before { display: none; }

.num { font-family: var(--f-mono); font-variant-numeric: tabular-nums; }

/* ---------- 按钮 ---------- */
.btn {
  --btn-bg: transparent;
  --btn-fg: var(--c-text);
  --btn-bd: var(--c-line-2);
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--s-3);
  min-height: 52px;
  padding: 0 var(--s-5);
  background: var(--btn-bg);
  color: var(--btn-fg);
  border: 1px solid var(--btn-bd);
  border-radius: var(--r-pill);
  font-family: var(--f-mono);
  font-size: var(--fs-xs);
  font-weight: 500;
  letter-spacing: .1em;
  text-transform: uppercase;
  cursor: pointer;
  overflow: hidden;
  isolation: isolate;
  transition: color var(--dur-fast) var(--ease-out),
              border-color var(--dur-fast) var(--ease-out),
              transform var(--dur-fast) var(--ease-out);
}

/* 悬停：背景自下而上擦除，而不是简单变亮 */
.btn::before {
  content: "";
  position: absolute; inset: 0; z-index: -1;
  background: var(--c-accent);
  transform: translateY(101%);
  transition: transform var(--dur-base) var(--ease-out);
}

.btn:hover, .btn:focus-visible {
  color: var(--c-void);
  border-color: var(--c-accent);
}

.btn:hover::before, .btn:focus-visible::before { transform: translateY(0); }

.btn:active { transform: translateY(1px); }

.btn--solid {
  --btn-bg: var(--c-accent);
  --btn-bd: var(--c-accent);
  color: var(--c-void);
  font-weight: 500;
  box-shadow: var(--sh-accent);
}

.btn--solid::before { background: var(--c-text); }
.btn--solid:hover, .btn--solid:focus-visible { color: var(--c-void); border-color: var(--c-text); }

.btn__arrow {
  transition: transform var(--dur-base) var(--ease-out);
}

.btn:hover .btn__arrow { transform: translateX(4px); }

/* 文字型链接：下划线由左向右扫过 */
.link {
  position: relative;
  display: inline-block;
  padding-bottom: 2px;
}

.link::after {
  content: "";
  position: absolute; left: 0; bottom: 0;
  width: 100%; height: 1px;
  background: currentColor;
  transform: scaleX(0);
  transform-origin: left;
  transition: transform var(--dur-base) var(--ease-out);
}

.link:hover::after, .link:focus-visible::after { transform: scaleX(1); }

/* ---------- 入场 / 滚动揭示 ---------- */
.reveal {
  opacity: 0;
  transform: translateY(26px);
  transition: opacity var(--dur-slow) var(--ease-out),
              transform var(--dur-slow) var(--ease-out);
  transition-delay: var(--rd, 0ms);
}

.reveal.is-in { opacity: 1; transform: none; }

/* 首屏编排：按 data-seq 错峰，间隔 90ms */
[data-seq="1"] { --rd: 0ms; }
[data-seq="2"] { --rd: 90ms; }
[data-seq="3"] { --rd: 180ms; }
[data-seq="4"] { --rd: 270ms; }
[data-seq="5"] { --rd: 360ms; }
[data-seq="6"] { --rd: 450ms; }

/* ---------- 无障碍 ---------- */
.sr-only {
  position: absolute; width: 1px; height: 1px;
  padding: 0; margin: -1px; overflow: hidden;
  clip: rect(0 0 0 0); white-space: nowrap; border: 0;
}

.skip-link {
  position: absolute; top: 8px; left: 8px;
  z-index: 100;
  padding: 10px 16px;
  background: var(--c-accent); color: var(--c-void);
  border-radius: var(--r-sm);
  font-family: var(--f-mono); font-size: var(--fs-xs);
  transform: translateY(-160%);
  transition: transform var(--dur-base) var(--ease-out);
}

.skip-link:focus { transform: translateY(0); }

/* ---------- 滚动条 ---------- */
* { scrollbar-width: thin; scrollbar-color: var(--c-line-2) transparent; }
*::-webkit-scrollbar { width: 10px; height: 10px; }
*::-webkit-scrollbar-thumb {
  background: var(--c-line-2);
  border-radius: var(--r-pill);
  border: 3px solid var(--c-bg);
}
*::-webkit-scrollbar-thumb:hover { background: var(--c-muted); }

/* ---------- 降级动效：reduce 下关闭全部位移与过渡 ---------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: .001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: .001ms !important;
    scroll-behavior: auto !important;
  }
  .reveal { opacity: 1; transform: none; }
  .cursor { display: none; }
}