/* ============================================================
   PA視訊中心 · /assets/site.css
   共享层：变量 / 复位 / 中文排版 / 页头 / 页脚 / 基础组件
   ============================================================ */

/* ---------- 1. 设计变量 ---------- */
:root{
  --deep:#05121F;
  --night:#0A1D2E;
  --slate:#16293B;
  --line:#2A4358;
  --mist:#E9F1F8;
  --silver:#A3B8CA;
  --orange:#FF6B2C;
  --cyan:#34E2D2;
  --glass:rgba(163,184,202,0.10);
  --warm:#FFF4EC;
  --amber:#F2B441;

  --font-sans:-apple-system,BlinkMacSystemFont,"Segoe UI","Noto Sans SC","HarmonyOS Sans SC","PingFang SC","Hiragino Sans GB","Microsoft YaHei",sans-serif;
  --font-mono:"JetBrains Mono","IBM Plex Mono",ui-monospace,SFMono-Regular,Menlo,Consolas,"Source Han Mono","Noto Sans Mono CJK SC",monospace;

  --maxw:1180px;
  --rail:72px;
  --measure:68ch;
  --pad:clamp(1.15rem,4vw,2.5rem);
  --dur:.2s;
  --ease:cubic-bezier(.2,.7,.3,1);
}

/* ---------- 2. 复位 ---------- */
*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;text-size-adjust:100%}
body{
  margin:0;
  background:var(--deep);
  color:var(--mist);
  font-family:var(--font-sans);
  font-size:clamp(1rem,.32vw + .95rem,1.0625rem);
  line-height:1.85;
  font-weight:400;
  -webkit-font-smoothing:antialiased;
  -moz-osx-font-smoothing:grayscale;
}
img,svg,video{display:block;max-width:100%}
button{font:inherit;color:inherit}
a{color:inherit;text-decoration:none}
ul,ol{margin:0;padding:0}
figure,blockquote{margin:0}
hr{border:0}

/* ---------- 3. 中文排版 ---------- */
h1,h2,h3,h4,h5{
  margin:0 0 .6em;
  font-weight:700;
  line-height:1.18;
  letter-spacing:-.02em;
  font-stretch:92%;
  text-wrap:balance;
  overflow-wrap:break-word;
}
h1{font-size:clamp(2.15rem,5.6vw,4rem)}
h2{font-size:clamp(1.6rem,3.4vw,2.5rem)}
h3{font-size:1.3125rem;letter-spacing:-.01em}
h4{font-size:1.0625rem;letter-spacing:0}
p{margin:0 0 1.15em;text-wrap:pretty}
p:last-child{margin-bottom:0}
strong{font-weight:700;color:var(--mist)}
small{font-size:.8125rem}
::selection{background:var(--orange);color:#05121F}

:focus-visible{outline:2px solid var(--cyan);outline-offset:3px;border-radius:2px}
#main-content{display:block;scroll-margin-top:1.5rem}

/* ---------- 4. 布局与排版工具 ---------- */
.container{
  width:100%;
  max-width:var(--maxw);
  margin-inline:auto;
  padding-inline:var(--pad);
}
.section{padding-block:clamp(3rem,7vw,6rem);position:relative}
.section--night{background:var(--night)}
.section--tight{padding-block:clamp(2rem,4.5vw,3.5rem)}
.rule{height:1px;background:var(--line);margin:0}

.display{
  display:block;
  font-size:clamp(3.25rem,9.5vw,6rem);
  line-height:.95;
  letter-spacing:-.035em;
  font-weight:700;
  margin:0 0 .35em;
}
.page-title{
  font-size:clamp(2.15rem,5.6vw,4rem);
  line-height:1.06;
  letter-spacing:-.028em;
  margin:0 0 .5em;
}
.section-title{font-size:clamp(1.6rem,3.4vw,2.5rem);margin:0 0 .5em}
.section-sub{font-size:1.75rem;line-height:1.35;letter-spacing:-.015em;margin:0 0 .6em}
.lede{font-size:1.125rem;line-height:1.85;color:var(--silver);max-width:var(--measure)}

.eyebrow,.chapter-no,.mono-tag{
  font-family:var(--font-mono);
  font-size:.6875rem;
  letter-spacing:.16em;
  text-transform:uppercase;
  font-weight:400;
}
.eyebrow{display:block;margin:0 0 .9rem;color:var(--silver)}
.chapter-no{
  display:inline-flex;
  align-items:center;
  gap:.55rem;
  margin:0 0 .9rem;
  color:var(--cyan);
  font-variant-numeric:tabular-nums;
}
.chapter-no::before{content:"";width:22px;height:1px;background:var(--cyan);display:inline-block}
.mono-tag{margin:0;color:var(--silver);font-variant-numeric:tabular-nums}

.prose{max-width:var(--measure)}
.prose p,.prose li{max-width:var(--measure)}
.prose h3{margin:2em 0 .6em}
.prose ul,.prose ol{padding-left:1.25em;margin:0 0 1.2em;list-style:revert}
.prose li{margin-bottom:.4em}
.prose a{color:var(--mist);border-bottom:1px solid var(--cyan);transition:color var(--dur)}
.prose a:hover{color:var(--cyan)}

.grid{display:grid;gap:clamp(1.25rem,3vw,2.5rem)}
.grid--2{grid-template-columns:repeat(2,minmax(0,1fr))}
.grid--3{grid-template-columns:repeat(3,minmax(0,1fr))}
.grid--5-7{grid-template-columns:5fr 7fr}
.grid--4-8{grid-template-columns:4fr 8fr}

.stack{display:grid;gap:var(--stack-gap,1.5rem)}

/* ---------- 5. 按钮 ---------- */
.btn{
  display:inline-flex;
  align-items:center;
  justify-content:center;
  gap:.55rem;
  padding:.72rem 1.35rem;
  border:1px solid var(--line);
  border-radius:2px;
  background:transparent;
  color:var(--mist);
  font-family:var(--font-sans);
  font-size:.9375rem;
  font-weight:700;
  letter-spacing:.02em;
  line-height:1.4;
  cursor:pointer;
  transition:background var(--dur) var(--ease),border-color var(--dur),color var(--dur),padding var(--dur) var(--ease);
}
.btn:hover{border-color:var(--cyan);color:var(--mist)}
.btn--signal{background:var(--orange);border-color:var(--orange);color:#05121F}
.btn--signal:hover{background:#ff8248;border-color:#ff8248;color:#05121F}
.btn--ghost{background:var(--glass);border-color:rgba(163,184,202,.28);color:var(--mist)}
.btn--ghost:hover{border-color:var(--cyan);color:var(--cyan)}

/* ---------- 6. Skip link / 进度 / 回顶 ---------- */
.skip-link{
  position:absolute;
  left:var(--pad);
  top:.6rem;
  z-index:120;
  padding:.8rem 1.2rem;
  background:var(--orange);
  color:#05121F;
  font-size:.875rem;
  font-weight:700;
  border-radius:2px;
  transform:translateY(-250%);
  transition:transform var(--dur) var(--ease);
}
.skip-link:focus{transform:translateY(0)}

.header-progress{
  position:fixed;
  inset:0 0 auto 0;
  height:2px;
  background:var(--cyan);
  transform:scaleX(0);
  transform-origin:0 50%;
  z-index:100;
  pointer-events:none;
}

.to-top{
  position:fixed;
  right:clamp(1rem,3vw,2rem);
  bottom:clamp(1rem,3vw,2rem);
  z-index:90;
  display:none;
  align-items:center;
  gap:.35rem;
  padding:.6rem .8rem;
  background:rgba(22,41,59,.94);
  border:1px solid var(--line);
  border-radius:2px;
  color:var(--mist);
  font-family:var(--font-mono);
  font-size:.75rem;
  letter-spacing:.12em;
  cursor:pointer;
  backdrop-filter:blur(10px);
  -webkit-backdrop-filter:blur(10px);
  transition:border-color var(--dur),color var(--dur);
}
.to-top[data-visible="true"]{display:inline-flex}
.to-top:hover{border-color:var(--cyan);color:var(--cyan)}

/* ---------- 7. 页头 ---------- */
.site-header{
  position:relative;
  background:var(--deep);
  color:var(--mist);
}

/* 7.1 状态条 */
.site-header__strip{background:var(--night);border-bottom:1px solid var(--line)}
.site-header__strip-inner{
  display:flex;
  flex-wrap:wrap;
  align-items:center;
  justify-content:space-between;
  gap:.25rem 1.5rem;
  padding-block:.5rem;
}
.console-line{
  display:inline-flex;
  align-items:baseline;
  gap:.5rem;
  margin:0;
  font-family:var(--font-mono);
  font-size:.6875rem;
  letter-spacing:.12em;
  font-variant-numeric:tabular-nums;
  white-space:nowrap;
}
.console-line__key{color:var(--silver);opacity:.72}
.console-line__val{color:var(--mist)}
.console-line--status{align-items:center}
.status-dot{
  width:6px;
  height:6px;
  border-radius:50%;
  background:var(--cyan);
  box-shadow:0 0 0 3px rgba(52,226,210,.16);
  animation:dot-pulse 3s ease-in-out infinite;
}
@keyframes dot-pulse{
  0%,100%{opacity:1;box-shadow:0 0 0 3px rgba(52,226,210,.16)}
  50%{opacity:.55;box-shadow:0 0 0 6px rgba(52,226,210,.05)}
}

/* 7.2 刊头 */
.masthead{
  position:relative;
  overflow:hidden;
  background:var(--deep);
  border-bottom:1px solid var(--line);
}
.masthead::before{
  content:"";
  position:absolute;
  inset:0;
  background-image:repeating-linear-gradient(90deg,rgba(42,67,88,.5) 0 1px,transparent 1px var(--rail));
  opacity:.45;
  pointer-events:none;
}
.masthead__inner{
  position:relative;
  display:grid;
  grid-template-columns:1fr auto 1fr;
  align-items:center;
  gap:1.5rem;
  padding-block:1.6rem 1.5rem;
}
.masthead__side{justify-self:start;max-width:16ch;line-height:1.7}
.masthead__side--end{justify-self:end;text-align:right}
.masthead__brand{
  display:grid;
  justify-items:center;
  gap:.45rem;
  text-align:center;
  min-width:0;
}
.masthead__title{
  display:block;
  font-size:clamp(1.85rem,4.6vw,2.9rem);
  font-weight:700;
  line-height:1.04;
  letter-spacing:.02em;
  color:var(--mist);
  transition:color var(--dur);
}
.masthead__tagline{
  display:block;
  font-size:.8125rem;
  letter-spacing:.2em;
  color:var(--silver);
  transition:color var(--dur);
}
.masthead__brand:hover .masthead__title{color:var(--warm)}
.masthead__brand:hover .masthead__tagline{color:var(--cyan)}

/* 7.3 导航条 */
.nav-bar{
  position:relative;
  background:var(--night);
  border-bottom:1px solid var(--line);
}
.nav-bar__inner{
  display:grid;
  grid-template-columns:1fr auto 1fr;
  align-items:center;
  gap:1rem;
  padding-block:.35rem;
}
.primary-nav{grid-column:2;justify-self:center;display:block}
.nav-list{
  display:flex;
  flex-wrap:wrap;
  align-items:center;
  justify-content:center;
  gap:0 clamp(.35rem,2.2vw,1.7rem);
  list-style:none;
  margin:0;
  padding:0;
}
.nav-list__item{position:relative}
.nav-link{
  position:relative;
  display:inline-block;
  padding:.95rem .3rem .9rem;
  color:var(--silver);
  font-size:.9375rem;
  letter-spacing:.04em;
  transition:color var(--dur);
}
.nav-link::after{
  content:"";
  position:absolute;
  left:.3rem;
  bottom:.42rem;
  width:14px;
  height:2px;
  background:var(--orange);
  opacity:0;
  transform:translateY(3px);
  transition:opacity var(--dur),transform var(--dur) var(--ease),background var(--dur);
}
.nav-link:hover{color:var(--mist)}
.nav-link:hover::after{opacity:1;transform:translateY(0);background:var(--cyan)}
.nav-link[aria-current="page"]{color:var(--mist);font-weight:700}
.nav-link[aria-current="page"]::after{opacity:1;transform:translateY(0);background:var(--orange)}

.nav-cta{grid-column:3;justify-self:end;white-space:nowrap}

.nav-toggle{
  display:none;
  grid-column:1;
  justify-self:start;
  align-items:center;
  gap:.55rem;
  padding:.5rem .7rem;
  background:transparent;
  border:1px solid var(--line);
  border-radius:2px;
  cursor:pointer;
  transition:border-color var(--dur);
}
.nav-toggle:hover{border-color:var(--cyan)}
.nav-toggle__bars{display:inline-grid;gap:4px}
.nav-toggle__bar{
  display:block;
  width:16px;
  height:1.5px;
  background:var(--cyan);
  transition:transform var(--dur) var(--ease),opacity var(--dur);
}
.nav-toggle__text{
  font-family:var(--font-mono);
  font-size:.6875rem;
  letter-spacing:.14em;
  color:var(--mist);
}
.nav-toggle[aria-expanded="true"] .nav-toggle__bar:nth-child(1){transform:translateY(5.5px) rotate(45deg)}
.nav-toggle[aria-expanded="true"] .nav-toggle__bar:nth-child(2){opacity:0}
.nav-toggle[aria-expanded="true"] .nav-toggle__bar:nth-child(3){transform:translateY(-5.5px) rotate(-45deg)}

@keyframes nav-in{
  from{opacity:0;transform:translateY(-4px)}
  to{opacity:1;transform:none}
}

@media (min-width:901px){
  .btn--signal:hover{padding-left:calc(1.35rem - 8px);padding-right:calc(1.35rem + 4px)}
}

/* ---------- 8. 页脚 ---------- */
.site-footer{
  background:var(--night);
  border-top:1px solid var(--line);
  color:var(--silver);
  font-size:.9375rem;
  line-height:1.8;
}
.footer-signal{
  height:8px;
  border-top:1px solid var(--line);
  background-image:repeating-linear-gradient(90deg,var(--line) 0 1px,transparent 1px 14px);
  opacity:.7;
}
.footer-grid{
  display:grid;
  grid-template-columns:1.7fr 1fr 1fr 1.15fr;
  gap:clamp(1.5rem,4vw,3rem);
  padding-block:clamp(2.5rem,5vw,3.75rem);
  align-items:start;
}
.footer-brand__title{
  margin:0 0 .6rem;
  font-size:1.5rem;
  font-weight:700;
  letter-spacing:.04em;
  line-height:1.2;
  color:var(--mist);
}
.footer-brand__tagline{margin:0 0 .8rem;color:var(--mist);font-size:.9375rem}
.footer-brand__note{margin:0;max-width:34ch;color:var(--silver);font-size:.875rem}
.footer-col__title{
  margin:0 0 .9rem;
  font-family:var(--font-mono);
  font-size:.6875rem;
  font-weight:400;
  letter-spacing:.18em;
  text-transform:uppercase;
  color:var(--cyan);
}
.footer-list{list-style:none;margin:0;padding:0;display:grid;gap:.55rem}
.footer-list__item{margin:0}
.footer-link{
  color:var(--silver);
  border-bottom:1px solid transparent;
  transition:color var(--dur),border-color var(--dur);
}
.footer-link:hover,.footer-link:focus-visible{color:var(--mist);border-bottom-color:var(--cyan)}
.footer-meta-text{
  font-family:var(--font-mono);
  font-size:.75rem;
  letter-spacing:.04em;
  color:var(--silver);
  word-break:break-word;
}
.footer-contact{
  display:grid;
  grid-template-columns:repeat(auto-fit,minmax(230px,1fr));
  gap:.4rem 2rem;
  padding-block:1.5rem;
  border-top:1px solid var(--line);
  border-bottom:1px solid var(--line);
}
.footer-contact__row{
  display:flex;
  flex-wrap:wrap;
  align-items:baseline;
  gap:.6rem;
  margin:0;
  min-width:0;
}
.footer-contact__key{
  font-family:var(--font-mono);
  font-size:.6875rem;
  letter-spacing:.14em;
  color:var(--silver);
  opacity:.78;
  min-width:4.5rem;
}
.footer-contact__val{color:var(--mist);font-size:.9375rem;word-break:break-word}
.footer-note{
  grid-column:1 / -1;
  margin:.9rem 0 0;
  max-width:62ch;
  font-size:.8125rem;
  color:var(--silver);
}
.footer-meta{
  display:flex;
  flex-wrap:wrap;
  align-items:center;
  justify-content:space-between;
  gap:.75rem 2rem;
  padding-block:1.4rem 1.6rem;
}
.footer-meta__legal{
  margin:0;
  font-family:var(--font-mono);
  font-size:.75rem;
  letter-spacing:.08em;
  color:var(--silver);
  font-variant-numeric:tabular-nums;
}
.footer-icp{color:var(--silver)}
.footer-legal-links{
  display:flex;
  flex-wrap:wrap;
  gap:.5rem 1.5rem;
  list-style:none;
  margin:0;
  padding:0;
  font-size:.8125rem;
}

/* ---------- 9. 基础组件 ---------- */
.breadcrumb{
  display:flex;
  flex-wrap:wrap;
  align-items:center;
  gap:.5rem;
  padding-block:.9rem;
  font-family:var(--font-mono);
  font-size:.75rem;
  letter-spacing:.08em;
  color:var(--silver);
}
.breadcrumb__link{color:var(--silver);border-bottom:1px solid transparent;transition:color var(--dur),border-color var(--dur)}
.breadcrumb__link:hover{color:var(--cyan);border-bottom-color:var(--cyan)}
.breadcrumb__sep{color:var(--line)}

.card{
  background:var(--slate);
  border:1px solid var(--line);
  border-radius:2px;
  padding:clamp(1.1rem,2.4vw,1.7rem);
  transition:border-color var(--dur),transform var(--dur) var(--ease);
}
.card:hover{border-color:var(--cyan);transform:translateY(-2px)}

.tag{
  display:inline-flex;
  align-items:center;
  gap:.4rem;
  padding:.3rem .55rem;
  background:rgba(163,184,202,.08);
  border:1px solid var(--line);
  border-radius:2px;
  font-family:var(--font-mono);
  font-size:.75rem;
  letter-spacing:.06em;
  color:var(--silver);
  transition:border-color var(--dur),color var(--dur),opacity var(--dur);
}
.tag:hover{border-color:var(--cyan);color:var(--mist)}

.glass-panel{
  background:var(--glass);
  border:1px solid rgba(163,184,202,.24);
  backdrop-filter:blur(12px);
  -webkit-backdrop-filter:blur(12px);
  border-radius:2px;
}

.figure{display:grid;gap:.7rem;margin:0}
.figure__frame{
  position:relative;
  overflow:hidden;
  aspect-ratio:16/10;
  border:1px solid var(--line);
  border-radius:2px;
  background:var(--slate);
}
.figure__frame::after{
  content:"";
  position:absolute;
  inset:0;
  border:1px solid rgba(52,226,210,.14);
  pointer-events:none;
}
.figure__img{width:100%;height:100%;object-fit:cover;display:block}
.figure__caption{
  font-family:var(--font-mono);
  font-size:.75rem;
  letter-spacing:.06em;
  color:var(--silver);
}
.figure--wide .figure__frame{aspect-ratio:21/9}
.figure--tall .figure__frame{aspect-ratio:3/4}

/* 左侧章节索引条（桌面 ≥1200px） */
.chapter-rail{
  position:fixed;
  left:0;
  top:0;
  bottom:0;
  width:var(--rail);
  z-index:50;
  display:none;
  flex-direction:column;
  justify-content:center;
  padding:0 .6rem;
  background:rgba(10,29,46,.6);
  border-right:1px solid var(--line);
  backdrop-filter:blur(6px);
  -webkit-backdrop-filter:blur(6px);
}
.chapter-rail__list{list-style:none;margin:0;padding:0;display:grid;gap:.9rem}
.chapter-rail__link{
  display:grid;
  gap:.1rem;
  padding:.2rem 0 .2rem .5rem;
  border-left:2px solid transparent;
  color:var(--silver);
  font-family:var(--font-mono);
  font-size:.6875rem;
  letter-spacing:.08em;
  line-height:1.5;
  transition:color var(--dur),border-color var(--dur);
}
.chapter-rail__no{color:var(--line);font-variant-numeric:tabular-nums;transition:color var(--dur)}
.chapter-rail__link:hover{color:var(--mist);border-left-color:var(--cyan)}
.chapter-rail__link[aria-current="true"]{color:var(--mist);border-left-color:var(--orange)}
.chapter-rail__link[aria-current="true"] .chapter-rail__no{color:var(--cyan)}

@media (min-width:1200px){
  .chapter-rail{display:flex}
}

/* ---------- 10. 响应式 ---------- */
@media (max-width:1100px){
  .footer-grid{grid-template-columns:1fr 1fr}
  .footer-brand{grid-column:1 / -1}
}

@media (max-width:900px){
  .masthead__inner{grid-template-columns:1fr;gap:.8rem;padding-block:1.25rem}
  .masthead__side{display:none}
  .masthead__tagline{letter-spacing:.12em}

  .nav-bar__inner{
    grid-template-columns:auto 1fr;
    gap:.75rem;
    padding-block:.6rem;
  }
  .nav-toggle{display:inline-flex}
  .nav-cta{grid-column:2;justify-self:end;font-size:.8125rem;padding:.55rem .85rem}
  .primary-nav{
    grid-column:1 / -1;
    justify-self:stretch;
    display:none;
    width:100%;
    margin-top:.55rem;
    border-top:1px solid var(--line);
    background:rgba(10,29,46,.97);
  }
  .primary-nav[data-open="true"]{display:block;animation:nav-in .18s var(--ease) both}
  .nav-list{flex-direction:column;align-items:stretch;gap:0}
  .nav-list__item{border-bottom:1px solid rgba(42,67,88,.55)}
  .nav-list__item:last-child{border-bottom:0}
  .nav-link{
    display:flex;
    align-items:center;
    justify-content:space-between;
    padding:.85rem .55rem .82rem;
    font-size:1rem;
  }
  .nav-link::after{display:none}
  .nav-link[aria-current="page"]{
    background:rgba(255,107,44,.1);
    box-shadow:inset 3px 0 0 var(--orange);
  }

  .grid--2,.grid--3,.grid--5-7,.grid--4-8{grid-template-columns:minmax(0,1fr)}
}

@media (max-width:720px){
  .site-header__strip-inner{gap:.2rem 1rem;justify-content:flex-start;padding-block:.45rem}
  .console-line{font-size:.625rem;letter-spacing:.08em}
  .console-line:last-child{margin-left:auto}
  .footer-grid{grid-template-columns:1fr;gap:1.75rem}
  .footer-meta{flex-direction:column;align-items:flex-start}
  .footer-legal-links{gap:.4rem 1.1rem}
  .to-top{font-size:.6875rem;padding:.5rem .65rem}
}

@media (max-width:420px){
  .masthead__title{letter-spacing:0}
  .nav-cta{font-size:.75rem;padding:.5rem .6rem}
}

/* ---------- 11. 降低动效 ---------- */
@media (prefers-reduced-motion:reduce){
  *,*::before,*::after{
    animation-duration:.001ms !important;
    animation-iteration-count:1 !important;
    transition-duration:.001ms !important;
    scroll-behavior:auto !important;
  }
  .card:hover{transform:none}
}