/* ============================================================
   奇亿测速 · 共享站点套件 /assets/site.css
   深空蓝基底 · 荧光青数据 · 信号橙行动 · 精密网格与直角
   ============================================================ */

/* ---------- 1. reset ---------- */
*,
*::before,
*::after { box-sizing: border-box; }

html {
  -webkit-text-size-adjust: 100%;
  text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: clamp(140px, 18vh, 190px);
}

body,
h1, h2, h3, h4, h5, h6,
p, figure, blockquote, dl, dd, ul, ol { margin: 0; }

ul, ol { padding: 0; }
:where(ul[class], ol[class]) { list-style: none; }

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

button {
  font: inherit;
  color: inherit;
  background: none;
  border: 0;
  padding: 0;
  cursor: pointer;
}

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

table { border-collapse: collapse; width: 100%; }

/* ---------- 2. 变量 ---------- */
:root {
  /* 色板 */
  --ink-900: #071426;   /* 午夜蓝 */
  --ink-800: #0B1F3A;   /* 深空蓝 */
  --ink-700: #243B55;   /* 石墨蓝 */
  --cyan: #00E5C3;      /* 荧光青 */
  --orange: #FF6B35;    /* 信号橙 */
  --paper: #F2EDE3;     /* 奶油纸 */
  --brown: #1A1410;     /* 深棕黑 */
  --slate: #6B7C93;     /* 灰蓝 */
  --slate-light: #A9B7C6;
  --mint: #E8FBF7;      /* 薄荷白 */

  /* 线 */
  --line: rgba(169, 183, 198, 0.20);
  --line-soft: rgba(169, 183, 198, 0.12);
  --line-cyan: rgba(0, 229, 195, 0.30);
  --line-orange: rgba(255, 107, 53, 0.42);

  /* 尺寸 */
  --shell: 1280px;
  --pad-x: clamp(16px, 4vw, 56px);
  --gap: clamp(16px, 2.4vw, 32px);
  --radius-capsule: 999px;
  --radius-sharp: 2px;

  /* 字体 */
  --font-display: "HarmonyOS Sans SC", "Noto Sans SC", "Source Han Sans SC", "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
  --font-body: "PingFang SC", "Noto Sans SC", "Source Han Sans SC", "Microsoft YaHei", system-ui, sans-serif;
  --font-mono: "JetBrains Mono", "Roboto Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, "Courier New", monospace;

  /* 动效 */
  --ease: cubic-bezier(0.22, 0.61, 0.36, 1);
  --shadow-island: 0 18px 44px -24px rgba(0, 0, 0, 0.92);
  --scroll-progress: 0;
}

/* ---------- 3. 中文基础排版 ---------- */
body {
  font-family: var(--font-body);
  font-size: clamp(15px, 1.05vw, 17px);
  line-height: 1.68;
  letter-spacing: 0.01em;
  color: var(--mint);
  background:
    radial-gradient(120% 70% at 82% -10%, rgba(0, 229, 195, 0.10), transparent 60%),
    radial-gradient(90% 60% at 6% 4%, rgba(255, 107, 53, 0.07), transparent 58%),
    var(--ink-900);
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 800;
  line-height: 1.16;
  letter-spacing: -0.01em;
  color: var(--mint);
  text-wrap: balance;
}

p { text-wrap: pretty; }

::selection {
  background: var(--cyan);
  color: var(--ink-900);
}

/* ---------- 4. 焦点 ---------- */
:where(a, button, [tabindex]):focus-visible {
  outline: 2px solid var(--cyan);
  outline-offset: 3px;
  border-radius: 4px;
}

:where(a, button):focus:not(:focus-visible) { outline: none; }

/* ---------- 5. skip link ---------- */
.skip-link {
  position: fixed;
  top: 10px;
  left: 50%;
  z-index: 300;
  transform: translate(-50%, -180%);
  padding: 11px 20px;
  border-radius: var(--radius-capsule);
  background: var(--cyan);
  color: var(--ink-900);
  font-family: var(--font-body);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.04em;
  transition: transform 0.26s var(--ease);
}

.skip-link:focus,
.skip-link:focus-visible {
  transform: translate(-50%, 0);
  outline-offset: 4px;
}

/* ---------- 6. 按钮 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 11px 20px;
  border: 1px solid transparent;
  border-radius: var(--radius-capsule);
  font-family: var(--font-body);
  font-size: 13.5px;
  font-weight: 700;
  letter-spacing: 0.03em;
  line-height: 1;
  white-space: nowrap;
  transition: background 0.24s var(--ease), color 0.24s var(--ease),
    border-color 0.24s var(--ease), transform 0.2s var(--ease);
}

.btn-primary {
  background: var(--orange);
  color: var(--ink-900);
  border-color: var(--orange);
}

.btn-primary:hover {
  background: #ff8557;
  border-color: #ff8557;
  transform: translateY(-1px);
}

.btn-ghost {
  background: rgba(0, 229, 195, 0.07);
  color: var(--cyan);
  border-color: var(--line-cyan);
}

.btn-ghost:hover {
  background: rgba(0, 229, 195, 0.16);
  color: var(--mint);
}

.btn-outline {
  background: transparent;
  color: var(--mint);
  border-color: var(--line);
}

.btn-outline:hover {
  border-color: var(--line-cyan);
  color: var(--cyan);
}

/* ---------- 7. 头部外壳 ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 90;
  padding: clamp(10px, 1.4vw, 18px) clamp(12px, 3vw, 40px) clamp(10px, 1.4vw, 16px);
  background: transparent;
}

.site-header::before {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 0;
  background: linear-gradient(
    180deg,
    rgba(7, 20, 38, 0.96) 0%,
    rgba(7, 20, 38, 0.78) 58%,
    rgba(7, 20, 38, 0) 100%
  );
  -webkit-backdrop-filter: blur(10px);
  backdrop-filter: blur(10px);
  -webkit-mask-image: linear-gradient(180deg, #000 0%, #000 62%, transparent 100%);
  mask-image: linear-gradient(180deg, #000 0%, #000 62%, transparent 100%);
  pointer-events: none;
}

/* 顶部滚动进度 */
.site-header::after {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  z-index: 3;
  height: 2px;
  width: calc(var(--scroll-progress, 0) * 100%);
  background: linear-gradient(90deg, var(--cyan) 0%, var(--orange) 100%);
  transition: width 0.12s linear;
  pointer-events: none;
}

.site-header > * {
  position: relative;
  z-index: 1;
}

/* ---------- 8. 第一栏：胶囊浮岛 ---------- */
.header-island {
  position: relative;
  display: flex;
  align-items: center;
  gap: clamp(10px, 1.8vw, 26px);
  max-width: var(--shell);
  margin-inline: auto;
  padding: 7px 8px 7px clamp(12px, 1.6vw, 20px);
  background: linear-gradient(120deg, rgba(11, 31, 58, 0.97) 0%, rgba(7, 20, 38, 0.92) 100%);
  border: 1px solid var(--line-cyan);
  border-radius: var(--radius-capsule);
  box-shadow: var(--shadow-island);
  transition: padding 0.3s var(--ease), box-shadow 0.3s var(--ease);
}

.site-header[data-scrolled] .header-island {
  padding-block: 4px;
  box-shadow: 0 14px 32px -22px rgba(0, 0, 0, 0.95);
}

/* 品牌簇 */
.brand-cluster {
  display: flex;
  align-items: center;
  gap: clamp(10px, 1.4vw, 18px);
  flex: 0 0 auto;
  min-width: 0;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  flex: 0 0 auto;
}

.brand-mark {
  position: relative;
  display: grid;
  place-items: center;
  width: 34px;
  height: 34px;
  flex: 0 0 auto;
  border: 1px solid var(--line-cyan);
  border-radius: var(--radius-capsule);
  background:
    radial-gradient(circle at 32% 30%, rgba(0, 229, 195, 0.55), rgba(0, 229, 195, 0) 68%),
    var(--ink-800);
  overflow: hidden;
}

.brand-mark::before {
  content: "";
  width: 16px;
  height: 2px;
  background: var(--cyan);
  box-shadow: 0 6px 0 -0.5px rgba(0, 229, 195, 0.55), 0 -6px 0 -0.5px rgba(0, 229, 195, 0.32);
  transform: rotate(-18deg);
}

.brand-text {
  display: grid;
  gap: 2px;
  min-width: 0;
}

.brand-name {
  font-family: var(--font-display);
  font-size: 15px;
  font-weight: 800;
  letter-spacing: 0.06em;
  line-height: 1.1;
  color: var(--mint);
}

.brand-latin {
  font-family: var(--font-mono);
  font-size: 9.5px;
  font-weight: 600;
  letter-spacing: 0.24em;
  line-height: 1;
  color: var(--cyan);
  opacity: 0.9;
}

.brand-tag {
  font-family: var(--font-mono);
  font-size: 10.5px;
  font-weight: 500;
  letter-spacing: 0.1em;
  color: var(--slate-light);
  padding-left: clamp(10px, 1.4vw, 18px);
  border-left: 1px solid var(--line-soft);
  white-space: nowrap;
}

/* 导航胶囊 */
.nav-capsule {
  flex: 1 1 auto;
  min-width: 0;
  display: flex;
  justify-content: center;
}

.nav-list {
  display: flex;
  align-items: center;
  gap: 2px;
}

.nav-item { flex: 0 0 auto; }

.nav-link {
  display: block;
  padding: 9px 13px;
  border-radius: var(--radius-capsule);
  font-size: 13.5px;
  font-weight: 500;
  letter-spacing: 0.02em;
  line-height: 1;
  color: var(--slate-light);
  white-space: nowrap;
  transition: color 0.22s var(--ease), background 0.22s var(--ease);
}

.nav-link:hover {
  color: var(--mint);
  background: rgba(0, 229, 195, 0.09);
}

.nav-link[aria-current="page"] {
  background: var(--cyan);
  color: var(--ink-900);
  font-weight: 700;
}

.nav-link[aria-current="page"]:hover {
  background: var(--cyan);
  color: var(--ink-900);
}

/* 右侧动作 */
.header-actions {
  display: flex;
  align-items: center;
  gap: 8px;
  flex: 0 0 auto;
  margin-left: auto;
}

.header-cta { padding: 10px 16px; font-size: 13px; }

/* 汉堡按钮 */
.nav-toggle {
  display: none;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  flex: 0 0 auto;
  border: 1px solid var(--line-cyan);
  border-radius: var(--radius-capsule);
  background: rgba(0, 229, 195, 0.06);
  transition: background 0.24s var(--ease), border-color 0.24s var(--ease);
}

.nav-toggle:hover { background: rgba(0, 229, 195, 0.16); }

.nav-toggle-box {
  position: relative;
  display: block;
  width: 18px;
  height: 12px;
}

.nav-toggle-bar {
  position: absolute;
  left: 0;
  width: 100%;
  height: 2px;
  background: var(--cyan);
  transition: transform 0.3s var(--ease), opacity 0.2s linear;
}

.nav-toggle-bar:nth-child(1) { top: 0; }
.nav-toggle-bar:nth-child(2) { top: 5px; }
.nav-toggle-bar:nth-child(3) { top: 10px; }

.site-header[data-open] .nav-toggle-bar:nth-child(1) {
  transform: translateY(5px) rotate(45deg);
}

.site-header[data-open] .nav-toggle-bar:nth-child(2) { opacity: 0; }

.site-header[data-open] .nav-toggle-bar:nth-child(3) {
  transform: translateY(-5px) rotate(-45deg);
}

/* ---------- 9. 第二栏：固定入口轨道 ---------- */
.header-rail {
  display: flex;
  align-items: center;
  gap: clamp(10px, 1.8vw, 22px);
  max-width: var(--shell);
  margin: 8px auto 0;
  padding: 7px clamp(10px, 1.4vw, 18px);
  border: 1px solid var(--line-soft);
  border-radius: var(--radius-sharp);
  background: linear-gradient(90deg, rgba(7, 20, 38, 0.92), rgba(36, 59, 85, 0.55));
  -webkit-backdrop-filter: blur(12px);
  backdrop-filter: blur(12px);
  overflow-x: auto;
  scrollbar-width: none;
}

.header-rail::-webkit-scrollbar { display: none; }

.rail-note {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  flex: 0 0 auto;
  font-family: var(--font-mono);
  font-size: 10px;
  font-weight: 600;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--slate);
  white-space: nowrap;
}

.rail-dot {
  width: 5px;
  height: 5px;
  border-radius: 50%;
  background: var(--orange);
  box-shadow: 0 0 0 3px rgba(255, 107, 53, 0.18);
}

.rail-links {
  display: flex;
  align-items: center;
  gap: 8px;
  flex: 0 0 auto;
}

.rail-link {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  padding: 6px 16px 6px 10px;
  font-size: 12.5px;
  font-weight: 700;
  letter-spacing: 0.03em;
  line-height: 1.2;
  color: var(--mint);
  background: rgba(36, 59, 85, 0.55);
  border-left: 2px solid var(--cyan);
  clip-path: polygon(0 0, 100% 0, calc(100% - 9px) 100%, 0 100%);
  white-space: nowrap;
  transition: background 0.22s var(--ease), color 0.22s var(--ease);
}

.rail-link:hover {
  background: rgba(0, 229, 195, 0.16);
  color: var(--mint);
}

.rail-link-accent {
  color: var(--orange);
  border-left-color: var(--orange);
  background: rgba(255, 107, 53, 0.10);
}

.rail-link-accent:hover {
  background: rgba(255, 107, 53, 0.22);
  color: #ffb092;
}

.rail-utility {
  display: flex;
  align-items: center;
  gap: clamp(8px, 1.4vw, 16px);
  margin-left: auto;
  flex: 0 0 auto;
  padding-left: clamp(8px, 1.4vw, 16px);
  border-left: 1px solid var(--line-soft);
}

.rail-utility-link {
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.16em;
  color: var(--slate-light);
  white-space: nowrap;
  transition: color 0.22s var(--ease);
}

.rail-utility-link:hover { color: var(--cyan); }

/* ---------- 10. 复制按钮 ---------- */
.copy-btn {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  font-family: var(--font-mono);
  font-size: 11.5px;
  font-weight: 600;
  letter-spacing: 0.08em;
  line-height: 1.4;
  color: var(--slate-light);
  border-bottom: 1px dashed transparent;
  transition: color 0.22s var(--ease), border-color 0.22s var(--ease);
}

.rail-copy {
  color: var(--slate-light);
  white-space: nowrap;
}

.copy-btn:hover {
  color: var(--cyan);
  border-bottom-color: var(--line-cyan);
}

.copy-btn.is-copied {
  color: var(--orange);
  border-bottom-color: var(--line-orange);
}

.rail-copy-dot {
  width: 4px;
  height: 4px;
  border-radius: 50%;
  background: currentColor;
  opacity: 0.8;
}

.copy-feedback {
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.08em;
}

/* ---------- 11. 移动端导航 ---------- */
@media (max-width: 1120px) {
  .nav-toggle { display: inline-flex; }

  .nav-capsule {
    position: absolute;
    top: calc(100% + 10px);
    left: 0;
    right: 0;
    z-index: 8;
    display: none;
    padding: 12px;
    background: rgba(7, 20, 38, 0.985);
    border: 1px solid var(--line-cyan);
    border-radius: 22px;
    box-shadow: var(--shadow-island);
    max-height: min(70vh, 520px);
    overflow-y: auto;
  }

  .site-header[data-open] .nav-capsule {
    display: block;
    animation: nav-drop 0.28s var(--ease) both;
  }

  .nav-list {
    flex-direction: column;
    align-items: stretch;
    gap: 4px;
  }

  .nav-link {
    padding: 13px 16px;
    border-radius: 14px;
    font-size: 15px;
  }

  .nav-link:hover { background: rgba(0, 229, 195, 0.10); }
}

@keyframes nav-drop {
  from { opacity: 0; transform: translateY(-8px); }
  to { opacity: 1; transform: translateY(0); }
}

@media (max-width: 880px) {
  .brand-tag { display: none; }
  .header-cta { display: none; }
  .rail-note { display: none; }
  .rail-utility { padding-left: 0; border-left: 0; }
}

@media (max-width: 560px) {
  .site-header {
    padding-inline: 10px;
    padding-top: 8px;
  }

  .brand-name { font-size: 14px; }
  .brand-latin { font-size: 8.5px; letter-spacing: 0.2em; }
  .brand-mark { width: 30px; height: 30px; }
  .rail-link { font-size: 11.5px; padding: 5px 14px 5px 9px; }
  .rail-utility-link { display: none; }
}

/* ---------- 12. 页脚 ---------- */
.site-footer {
  position: relative;
  margin-top: clamp(56px, 9vw, 120px);
  background: var(--ink-900);
  border-top: 1px solid var(--line-cyan);
  color: var(--slate-light);
  overflow: hidden;
}

.site-footer::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(169, 183, 198, 0.07) 1px, transparent 1px),
    linear-gradient(90deg, rgba(169, 183, 198, 0.07) 1px, transparent 1px);
  background-size: 52px 52px;
  -webkit-mask-image: linear-gradient(180deg, rgba(0, 0, 0, 0.95), transparent 72%);
  mask-image: linear-gradient(180deg, rgba(0, 0, 0, 0.95), transparent 72%);
  pointer-events: none;
}

.site-footer::after {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 2px;
  background: linear-gradient(
    90deg,
    var(--cyan) 0%,
    rgba(0, 229, 195, 0.1) 46%,
    rgba(255, 107, 53, 0.9) 88%,
    transparent 100%
  );
  opacity: 0.75;
  pointer-events: none;
}

.footer-inner {
  position: relative;
  z-index: 1;
  max-width: var(--shell);
  margin-inline: auto;
  padding: clamp(40px, 6vw, 76px) var(--pad-x) clamp(26px, 3.4vw, 44px);
  display: grid;
  grid-template-columns: minmax(230px, 1fr) minmax(0, 1.5fr) minmax(228px, 0.95fr);
  gap: clamp(26px, 4vw, 56px);
  align-items: start;
}

.footer-brand {
  display: grid;
  gap: 18px;
  align-content: start;
}

.footer-brand-line {
  font-family: var(--font-display);
  font-size: clamp(16px, 1.5vw, 20px);
  font-weight: 800;
  line-height: 1.45;
  letter-spacing: 0.01em;
  color: var(--mint);
  max-width: 22ch;
}

.footer-fixed {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.footer-fixed-link {
  display: inline-flex;
  align-items: center;
  padding: 7px 15px 7px 10px;
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.06em;
  line-height: 1.2;
  color: var(--cyan);
  background: rgba(0, 229, 195, 0.07);
  border-left: 2px solid var(--cyan);
  clip-path: polygon(0 0, 100% 0, calc(100% - 8px) 100%, 0 100%);
  white-space: nowrap;
  transition: background 0.22s var(--ease), color 0.22s var(--ease);
}

.footer-fixed-link:hover {
  background: rgba(0, 229, 195, 0.2);
  color: var(--mint);
}

.footer-cols {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(112px, 1fr));
  gap: clamp(18px, 2.6vw, 34px);
}

.footer-col { min-width: 0; }

.footer-col-title {
  font-family: var(--font-mono);
  font-size: 10px;
  font-weight: 700;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  line-height: 1;
  color: var(--slate);
  padding-bottom: 11px;
  margin-bottom: 13px;
  border-bottom: 1px solid var(--line-soft);
}

.footer-list {
  display: grid;
  gap: 9px;
}

.footer-link {
  display: inline-block;
  font-size: 13.5px;
  line-height: 1.5;
  color: var(--slate-light);
  transition: color 0.22s var(--ease), transform 0.22s var(--ease);
}

.footer-link:hover {
  color: var(--cyan);
  transform: translateX(3px);
}

.footer-contact {
  display: grid;
  gap: 15px;
  align-content: start;
  padding-left: clamp(0px, 2vw, 26px);
  border-left: 1px solid var(--line-soft);
}

.footer-contact-item { display: grid; gap: 5px; }

.footer-label {
  font-family: var(--font-mono);
  font-size: 9.5px;
  font-weight: 700;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--slate);
}

.footer-value {
  font-size: 13px;
  line-height: 1.6;
  color: var(--mint);
}

.footer-value--muted {
  font-size: 12.5px;
  line-height: 1.7;
  color: var(--slate-light);
}

.footer-copy-btn { font-size: 12.5px; }

.footer-base {
  position: relative;
  z-index: 1;
  max-width: var(--shell);
  margin-inline: auto;
  padding: 16px var(--pad-x) 28px;
  border-top: 1px solid var(--line-soft);
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px 26px;
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.05em;
  color: var(--slate);
}

.footer-copy { color: var(--slate); }
.footer-icp { color: var(--slate); }

@media (max-width: 1040px) {
  .footer-inner {
    grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  }

  .footer-contact {
    grid-column: 1 / -1;
    grid-template-columns: repeat(auto-fit, minmax(190px, 1fr));
    padding-left: 0;
    padding-top: 22px;
    border-left: 0;
    border-top: 1px solid var(--line-soft);
  }
}

@media (max-width: 680px) {
  .footer-inner {
    grid-template-columns: minmax(0, 1fr);
    gap: 30px;
  }

  .footer-cols { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .footer-contact { grid-template-columns: minmax(0, 1fr); }
  .footer-base { font-size: 10.5px; letter-spacing: 0.04em; }
}

/* ---------- 13. 通用版式与网格 ---------- */
.shell {
  width: 100%;
  max-width: var(--shell);
  margin-inline: auto;
  padding-inline: var(--pad-x);
}

.editorial-grid {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: var(--gap);
  align-items: start;
}

.display {
  font-family: var(--font-display);
  font-weight: 800;
  line-height: 1.04;
  letter-spacing: -0.02em;
  color: var(--mint);
}

.num {
  font-family: var(--font-mono);
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  letter-spacing: -0.03em;
  line-height: 1;
  color: var(--cyan);
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-mono);
  font-size: 10.5px;
  font-weight: 600;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  line-height: 1;
  color: var(--cyan);
}

.eyebrow-dot {
  width: 5px;
  height: 5px;
  border-radius: 50%;
  background: var(--orange);
  box-shadow: 0 0 0 3px rgba(255, 107, 53, 0.16);
  flex: 0 0 auto;
}

.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 10px;
  border: 1px solid var(--line-cyan);
  border-radius: var(--radius-sharp);
  background: rgba(0, 229, 195, 0.06);
  font-family: var(--font-mono);
  font-size: 10.5px;
  font-weight: 600;
  letter-spacing: 0.1em;
  line-height: 1;
  color: var(--cyan);
  white-space: nowrap;
}

.hairline {
  height: 1px;
  border: 0;
  background: linear-gradient(
    90deg,
    var(--line-cyan) 0%,
    rgba(169, 183, 198, 0.12) 58%,
    transparent 100%
  );
}

.section-head {
  display: grid;
  gap: 10px;
  align-content: start;
}

.section-index {
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.24em;
  color: var(--orange);
}

.section-title {
  font-family: var(--font-display);
  font-size: clamp(26px, 3.4vw, 44px);
  font-weight: 800;
  line-height: 1.14;
  letter-spacing: -0.015em;
  color: var(--mint);
}

/* ---------- 14. 面包屑 ---------- */
.breadcrumb {
  max-width: var(--shell);
  margin-inline: auto;
  padding: 20px var(--pad-x) 0;
}

.breadcrumb-list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 7px;
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 500;
  letter-spacing: 0.08em;
  color: var(--slate);
}

.breadcrumb-item {
  display: inline-flex;
  align-items: center;
  gap: 7px;
}

.breadcrumb-link {
  color: var(--slate-light);
  border-bottom: 1px solid transparent;
  transition: color 0.22s var(--ease), border-color 0.22s var(--ease);
}

.breadcrumb-link:hover {
  color: var(--cyan);
  border-bottom-color: var(--line-cyan);
}

.breadcrumb-sep {
  color: var(--slate);
  opacity: 0.55;
}

.breadcrumb-current {
  color: var(--cyan);
  font-weight: 700;
}

/* ---------- 15. 图片容器基础规则 ---------- */
.media-frame {
  position: relative;
  display: block;
  width: 100%;
  aspect-ratio: 16 / 10;
  overflow: hidden;
  border: 1px solid rgba(169, 183, 198, 0.18);
  border-radius: var(--radius-sharp);
  background:
    linear-gradient(158deg, var(--ink-700) 0%, var(--ink-900) 68%),
    var(--ink-800);
}

.media-frame::after {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(0, 229, 195, 0.08) 1px, transparent 1px),
    linear-gradient(90deg, rgba(0, 229, 195, 0.08) 1px, transparent 1px);
  background-size: 34px 34px;
  opacity: 0.7;
  pointer-events: none;
}

.media-frame > img,
.media-frame > svg,
.media-frame > picture {
  position: relative;
  z-index: 1;
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.media-frame--wide { aspect-ratio: 21 / 9; }
.media-frame--tall { aspect-ratio: 4 / 5; }
.media-frame--square { aspect-ratio: 1 / 1; }
.media-frame--paper {
  background: linear-gradient(158deg, #fbf7ef 0%, var(--paper) 100%);
  border-color: rgba(26, 20, 16, 0.14);
}

.media-caption {
  margin-top: 10px;
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 500;
  line-height: 1.55;
  letter-spacing: 0.05em;
  color: var(--slate);
}

/* ---------- 16. 返回顶部 ---------- */
.to-top {
  position: fixed;
  right: clamp(14px, 2.2vw, 30px);
  bottom: clamp(16px, 2.4vw, 32px);
  z-index: 120;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 16px 10px 14px;
  border: 1px solid var(--line-cyan);
  border-radius: var(--radius-capsule);
  background: rgba(7, 20, 38, 0.94);
  -webkit-backdrop-filter: blur(12px);
  backdrop-filter: blur(12px);
  color: var(--cyan);
  font-family: var(--font-mono);
  font-size: 10.5px;
  font-weight: 700;
  letter-spacing: 0.18em;
  opacity: 0;
  visibility: hidden;
  transform: translateY(12px);
  transition: opacity 0.28s var(--ease), transform 0.28s var(--ease),
    visibility 0.28s var(--ease), background 0.24s var(--ease);
}

.to-top[data-visible] {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.to-top:hover {
  background: rgba(0, 229, 195, 0.16);
  color: var(--mint);
}

.to-top-arrow {
  position: relative;
  display: block;
  width: 9px;
  height: 9px;
  border-left: 2px solid currentColor;
  border-top: 2px solid currentColor;
  transform: rotate(45deg) translate(1px, 1px);
}

.to-top-text { line-height: 1; }

/* ---------- 17. 纸面阅读区（页面可复用） ---------- */
.paper-surface {
  background: var(--paper);
  color: var(--brown);
}

.paper-surface :where(h1, h2, h3, h4) { color: var(--ink-800); }

.paper-surface :where(.eyebrow) { color: var(--orange); }

/* ---------- 18. 动效降级 ---------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }

  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
    scroll-behavior: auto !important;
  }

  .site-header::after { transition: none; }
  .to-top { transform: none; }
}