/* ============================================================
   博亚娱乐中心 · site.css
   技术蓝图 × 冰城夜场 · 深空黑 / 冰蓝 / 霓虹品红 / 电光青
   ============================================================ */

/* ---------- 1. TOKENS ---------- */
:root{
  --by-void:#060A12;
  --by-surface:#0E1830;
  --by-line:#1E2C48;
  --by-ice:#7FD4FF;
  --by-hot:#FF2E8B;
  --by-cyan:#00F0E0;
  --by-text:#EAF4FF;
  --by-muted:#93A9C6;
  --by-violet:#7A5CFF;
  --by-amber:#FFB020;

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

  --by-max:1440px;
  --by-gutter:clamp(16px,4vw,48px);
  --by-border:3px solid var(--by-line);
  --by-shadow-hard:12px 12px 0 rgba(3,7,14,.78);
  --by-ease:cubic-bezier(.2,.7,.3,1);
}

/* ---------- 2. RESET ---------- */
*,*::before,*::after{box-sizing:border-box}
html{
  -webkit-text-size-adjust:100%;
  background:var(--by-void);
  scroll-behavior:smooth;
  scroll-padding-top:110px;
}
body{
  margin:0;
  min-height:100vh;
  position:relative;
  overflow-x:hidden;
  background:transparent;
  color:var(--by-text);
  font-family:var(--by-font-sans);
  font-size:17px;
  line-height:1.75;
  -webkit-font-smoothing:antialiased;
  text-rendering:optimizeLegibility;
}
/* 蓝图网格：固定不滚动，首屏密、向下稀 */
body::before{
  content:"";
  position:fixed;
  inset:0;
  z-index:-1;
  pointer-events:none;
  background-color:var(--by-void);
  background-image:
    linear-gradient(to right,rgba(127,212,255,.075) 1px,transparent 1px),
    linear-gradient(to bottom,rgba(127,212,255,.075) 1px,transparent 1px),
    linear-gradient(to right,rgba(127,212,255,.14) 1px,transparent 1px),
    linear-gradient(to bottom,rgba(127,212,255,.14) 1px,transparent 1px);
  background-size:32px 32px,32px 32px,160px 160px,160px 160px;
}
h1,h2,h3,h4,h5,p,figure,blockquote{margin:0}
ul,ol{margin:0;padding:0;list-style:none}
img,svg,video,picture{display:block;max-width:100%}
a{color:inherit;text-decoration:none}
button{font:inherit;color:inherit;background:none;border:0;cursor:pointer}
table{border-collapse:collapse;width:100%}
::selection{background:var(--by-cyan);color:var(--by-void)}
:focus-visible{outline:2px solid var(--by-ice);outline-offset:3px}

/* ---------- 3. 容器与网格 ---------- */
.by-container{
  width:100%;
  max-width:var(--by-max);
  margin-inline:auto;
  padding-inline:var(--by-gutter);
}
.by-grid{
  display:grid;
  grid-template-columns:repeat(12,minmax(0,1fr));
  gap:clamp(16px,2.2vw,32px);
}
.by-col-3{grid-column:span 3}
.by-col-4{grid-column:span 4}
.by-col-5{grid-column:span 5}
.by-col-6{grid-column:span 6}
.by-col-7{grid-column:span 7}
.by-col-8{grid-column:span 8}
.by-col-9{grid-column:span 9}
.by-col-12{grid-column:span 12}

/* ---------- 4. 排版基元 ---------- */
.by-lede{
  max-width:62ch;
  font-size:clamp(17px,1.5vw,20px);
  line-height:1.8;
  color:var(--by-muted);
}
.by-lede strong{color:var(--by-text);font-weight:700}
.by-meta{
  font-family:var(--by-font-mono);
  font-size:12px;
  letter-spacing:.06em;
  color:var(--by-muted);
}
.by-annotation{
  writing-mode:vertical-rl;
  font-family:var(--by-font-mono);
  font-size:12px;
  letter-spacing:.24em;
  color:var(--by-ice);
  padding-inline-start:8px;
  border-inline-start:1px solid var(--by-ice);
  align-self:stretch;
}
.by-rule{height:1px;border:0;background:var(--by-line);margin:0}

/* ---------- 5. 章节题头 ---------- */
.by-section{padding-block:clamp(48px,7vw,104px)}
.by-section__head{
  display:grid;
  grid-template-columns:auto minmax(0,1fr) auto;
  gap:clamp(12px,2vw,28px);
  align-items:end;
  padding-bottom:16px;
  margin-bottom:clamp(24px,3.4vw,46px);
  border-bottom:1px solid var(--by-line);
}
.by-section__num{
  font-family:var(--by-font-mono);
  font-size:13px;
  letter-spacing:.2em;
  color:var(--by-ice);
}
.by-section__title{
  font-weight:800;
  font-size:clamp(26px,3.6vw,46px);
  line-height:1.05;
  letter-spacing:-.01em;
  color:var(--by-text);
}
.by-section__kicker{
  font-family:var(--by-font-mono);
  font-size:11.5px;
  letter-spacing:.16em;
  text-transform:uppercase;
  color:var(--by-muted);
  white-space:nowrap;
}

/* ---------- 6. 按钮 ---------- */
.by-btn{
  display:inline-flex;
  align-items:center;
  gap:8px;
  padding:11px 18px;
  border:2px solid var(--by-ice);
  background:transparent;
  color:var(--by-text);
  font-family:var(--by-font-mono);
  font-size:12.5px;
  font-weight:600;
  letter-spacing:.1em;
  line-height:1;
  transition:transform .18s var(--by-ease),box-shadow .18s var(--by-ease),
             background-color .18s ease,color .18s ease,border-color .18s ease;
}
.by-btn:hover{
  background:var(--by-ice);
  color:var(--by-void);
  border-color:var(--by-ice);
  transform:translate(-2px,-2px);
  box-shadow:4px 4px 0 var(--by-line);
}
.by-btn--hot{
  background:var(--by-hot);
  color:var(--by-void);
  border-color:var(--by-hot);
  font-weight:800;
}
.by-btn--hot:hover{
  background:var(--by-cyan);
  border-color:var(--by-cyan);
  color:var(--by-void);
  box-shadow:4px 4px 0 var(--by-hot);
}
.by-btn--ghost{
  border-color:var(--by-line);
  color:var(--by-muted);
}
.by-btn--ghost:hover{
  background:rgba(127,212,255,.08);
  border-color:var(--by-ice);
  color:var(--by-text);
  transform:none;
  box-shadow:none;
}
.by-header__cta{padding:9px 16px}

/* ---------- 7. 卡片 / 面板 / 标签 ---------- */
.by-card{
  position:relative;
  background:var(--by-surface);
  border:var(--by-border);
  padding:clamp(20px,2.4vw,30px);
  transition:border-color .2s ease,transform .2s var(--by-ease),box-shadow .2s var(--by-ease);
}
.by-card:hover{
  border-color:var(--by-cyan);
  transform:translateY(-4px);
  box-shadow:var(--by-shadow-hard);
}
.by-card__corner{
  position:absolute;
  top:0;
  left:0;
  padding:5px 12px;
  background:var(--by-ice);
  color:var(--by-void);
  font-family:var(--by-font-mono);
  font-size:11px;
  font-weight:700;
  letter-spacing:.12em;
  line-height:1.4;
}
.by-card__title{
  font-size:20px;
  font-weight:800;
  letter-spacing:-.01em;
  line-height:1.3;
}
.by-card__text{
  margin-top:10px;
  font-size:15px;
  line-height:1.7;
  color:var(--by-muted);
}
.by-panel{
  background:var(--by-surface);
  border:var(--by-border);
  padding:clamp(20px,3vw,36px);
}
.by-tag{
  display:inline-flex;
  align-items:center;
  gap:6px;
  padding:4px 10px;
  border:1px solid var(--by-line);
  background:rgba(14,24,48,.82);
  color:var(--by-muted);
  font-family:var(--by-font-mono);
  font-size:11.5px;
  letter-spacing:.08em;
  line-height:1.5;
}
.by-tag--ice{color:var(--by-ice);border-color:rgba(127,212,255,.45)}
.by-tag--hot{color:var(--by-hot);border-color:rgba(255,46,139,.5)}
.by-tag--cyan{color:var(--by-cyan);border-color:rgba(0,240,224,.5)}
.by-tag--violet{color:var(--by-violet);border-color:rgba(122,92,255,.55)}
.by-tag--amber{color:var(--by-amber);border-color:rgba(255,176,32,.55)}
.by-kv{
  display:grid;
  grid-template-columns:auto minmax(0,1fr);
  gap:8px 18px;
  font-family:var(--by-font-mono);
  font-size:13px;
  letter-spacing:.03em;
}
.by-kv dt{color:var(--by-muted)}
.by-kv dd{margin:0;color:var(--by-text)}
.by-note{
  display:flex;
  gap:12px;
  align-items:flex-start;
  padding:14px 18px;
  border:1px solid rgba(255,176,32,.45);
  border-left:3px solid var(--by-amber);
  background:rgba(255,176,32,.06);
  font-size:14.5px;
  line-height:1.7;
}
.by-note__label{
  flex:0 0 auto;
  font-family:var(--by-font-mono);
  font-size:11.5px;
  letter-spacing:.14em;
  color:var(--by-amber);
}

/* ---------- 8. 面包屑 ---------- */
.by-crumbs{
  display:flex;
  flex-wrap:wrap;
  align-items:center;
  gap:8px;
  padding-block:18px;
  font-family:var(--by-font-mono);
  font-size:12px;
  letter-spacing:.06em;
  color:var(--by-muted);
}
.by-crumbs li{display:flex;align-items:center;gap:8px}
.by-crumbs li+li::before{content:"/";color:var(--by-line)}
.by-crumbs a{color:var(--by-ice)}
.by-crumbs a:hover{color:var(--by-cyan)}

/* ---------- 9. 图片容器（页面阶段放占位） ---------- */
.by-media{
  position:relative;
  display:block;
  overflow:hidden;
  aspect-ratio:16/9;
  border:var(--by-border);
  background:var(--by-surface);
}
.by-media img,.by-media video,.by-media picture{
  width:100%;
  height:100%;
  object-fit:cover;
}
.by-media__grid{
  position:absolute;
  inset:0;
  pointer-events:none;
  background-image:
    linear-gradient(to right,rgba(127,212,255,.16) 1px,transparent 1px),
    linear-gradient(to bottom,rgba(127,212,255,.16) 1px,transparent 1px);
  background-size:40px 40px;
  mix-blend-mode:screen;
}
.by-media__tag{
  position:absolute;
  left:0;
  bottom:0;
  padding:6px 14px;
  background:var(--by-hot);
  color:var(--by-void);
  font-family:var(--by-font-mono);
  font-size:11.5px;
  font-weight:700;
  letter-spacing:.1em;
}
.by-media--wide{aspect-ratio:21/9}
.by-media--tall{aspect-ratio:4/5}
.by-media--square{aspect-ratio:1/1}

/* ---------- 10. 头部 ---------- */
.by-header{
  position:sticky;
  top:0;
  z-index:80;
  background:rgba(6,10,18,.96);
  border-top:3px solid var(--by-line);
  border-bottom:1px solid var(--by-line);
  backdrop-filter:blur(8px);
  -webkit-backdrop-filter:blur(8px);
  transition:box-shadow .3s ease;
}
.by-header[data-scrolled="true"]{
  border-bottom-color:var(--by-ice);
  box-shadow:0 14px 26px rgba(3,7,14,.6);
}
.by-skip{
  position:absolute;
  left:12px;
  top:-72px;
  z-index:100;
  padding:10px 16px;
  background:var(--by-cyan);
  color:var(--by-void);
  border:2px solid var(--by-void);
  font-family:var(--by-font-mono);
  font-size:13px;
  font-weight:700;
  letter-spacing:.06em;
  transition:top .2s var(--by-ease);
}
.by-skip:focus{top:8px}

/* 系统条 */
.by-header__bar{
  max-height:64px;
  overflow:hidden;
  border-bottom:1px solid var(--by-line);
  transition:max-height .35s var(--by-ease),opacity .28s ease,border-color .3s ease;
}
.by-header[data-scrolled="true"] .by-header__bar{
  max-height:0;
  opacity:0;
  border-bottom-color:transparent;
}
.by-header__bar-inner{
  display:flex;
  align-items:center;
  gap:clamp(12px,2.5vw,36px);
  min-height:52px;
  font-family:var(--by-font-mono);
  font-size:12px;
  letter-spacing:.06em;
}
.by-brand{
  display:flex;
  align-items:center;
  gap:10px;
  flex:0 0 auto;
}
.by-brand__mark{
  display:grid;
  place-items:center;
  width:34px;
  height:34px;
  background:var(--by-hot);
  color:var(--by-void);
  font-family:var(--by-font-mono);
  font-size:13px;
  font-weight:800;
  letter-spacing:.02em;
  box-shadow:3px 3px 0 var(--by-ice);
}
.by-brand__name{
  font-family:var(--by-font-sans);
  font-size:18px;
  font-weight:900;
  letter-spacing:.02em;
  color:var(--by-text);
  white-space:nowrap;
}
.by-brand__sub{
  display:none;
  color:var(--by-muted);
  font-size:10px;
  letter-spacing:.2em;
  text-transform:uppercase;
  white-space:nowrap;
}
.by-status{
  display:flex;
  align-items:center;
  gap:8px;
  margin-left:auto;
  min-width:0;
  color:var(--by-muted);
  font-size:11.5px;
  letter-spacing:.04em;
}
.by-status__dot{
  flex:0 0 auto;
  width:8px;
  height:8px;
  border-radius:50%;
  background:var(--by-cyan);
  animation:by-pulse 4.6s ease-in-out infinite;
}
.by-status__text{
  overflow:hidden;
  text-overflow:ellipsis;
  white-space:nowrap;
}
.by-header__cmd{flex:0 0 auto}
.by-badge{
  display:inline-block;
  padding:4px 10px;
  border:1px solid var(--by-line);
  background:var(--by-surface);
  color:var(--by-ice);
  font-family:var(--by-font-mono);
  font-size:11px;
  letter-spacing:.1em;
  white-space:nowrap;
}
@keyframes by-pulse{
  0%,100%{opacity:.5;box-shadow:0 0 0 0 rgba(0,240,224,.55)}
  50%{opacity:1;box-shadow:0 0 0 6px rgba(0,240,224,0)}
}

/* 导航行 */
.by-header__nav-row{position:relative}
.by-header__nav-inner{
  display:flex;
  align-items:stretch;
  justify-content:space-between;
  gap:16px;
}
.by-nav{display:flex;align-items:stretch;min-width:0}
.by-nav__list{display:flex;align-items:stretch;gap:2px}
.by-nav__item{display:flex}
.by-nav__link{
  position:relative;
  display:flex;
  align-items:baseline;
  gap:6px;
  padding:14px 12px 13px;
  border-bottom:2px solid transparent;
  color:var(--by-muted);
  font-family:var(--by-font-mono);
  font-size:12.5px;
  letter-spacing:.08em;
  white-space:nowrap;
  transition:color .2s ease,background-color .2s ease,border-color .2s ease;
}
.by-nav__link:hover{
  color:var(--by-text);
  background:rgba(127,212,255,.07);
}
.by-nav__index{
  font-size:10px;
  letter-spacing:.06em;
  color:var(--by-ice);
  opacity:.85;
}
.by-nav__link[aria-current="page"]{
  color:var(--by-text);
  border-bottom-color:var(--by-cyan);
}
.by-nav__link[aria-current="page"] .by-nav__index{color:var(--by-cyan);opacity:1}
.by-header__actions{
  display:flex;
  align-items:center;
  gap:10px;
  flex:0 0 auto;
}

/* 移动菜单按钮 */
.by-nav-toggle{
  display:none;
  align-items:center;
  gap:9px;
  padding:11px 14px;
  border:2px solid var(--by-line);
  color:var(--by-text);
  font-family:var(--by-font-mono);
  font-size:12px;
  letter-spacing:.12em;
  transition:border-color .2s ease,color .2s ease;
}
.by-nav-toggle:hover{border-color:var(--by-ice);color:var(--by-ice)}
.by-nav-toggle__bars{
  position:relative;
  width:16px;
  height:2px;
  background:currentColor;
}
.by-nav-toggle__bars::before,
.by-nav-toggle__bars::after{
  content:"";
  position:absolute;
  left:0;
  width:16px;
  height:2px;
  background:currentColor;
  transition:transform .22s var(--by-ease);
}
.by-nav-toggle__bars::before{top:-5px}
.by-nav-toggle__bars::after{top:5px}
.by-nav-toggle[aria-expanded="true"]{
  border-color:var(--by-cyan);
  color:var(--by-cyan);
}
.by-nav-toggle[aria-expanded="true"] .by-nav-toggle__bars{background:transparent}
.by-nav-toggle[aria-expanded="true"] .by-nav-toggle__bars::before{transform:translateY(5px) rotate(45deg)}
.by-nav-toggle[aria-expanded="true"] .by-nav-toggle__bars::after{transform:translateY(-5px) rotate(-45deg)}

/* 滚动进度 */
.by-progress{
  position:absolute;
  left:0;
  bottom:0;
  z-index:2;
  width:100%;
  height:2px;
  transform:scaleX(0);
  transform-origin:0 50%;
  pointer-events:none;
  background:linear-gradient(90deg,var(--by-cyan) 0%,var(--by-ice) 55%,var(--by-hot) 100%);
}

/* ---------- 11. 页脚 ---------- */
.by-footer{
  position:relative;
  margin-top:clamp(64px,9vw,140px);
  border-top:1px solid var(--by-ice);
  background:var(--by-void);
  overflow:hidden;
}
.by-footer::after{
  content:"";
  position:absolute;
  inset:0;
  pointer-events:none;
  background:repeating-linear-gradient(
    115deg,
    transparent 0 130px,
    rgba(255,46,139,.05) 130px 134px,
    transparent 134px 340px
  );
}
.by-footer .by-container{position:relative;z-index:1}
.by-footer__grid{
  display:grid;
  grid-template-columns:1fr;
  gap:clamp(26px,4vw,56px);
  padding:clamp(40px,6vw,72px) 0 clamp(28px,4vw,44px);
}
.by-footer__brand{
  font-size:clamp(24px,3vw,34px);
  font-weight:900;
  line-height:1.1;
  letter-spacing:-.01em;
}
.by-footer__line{
  margin-top:10px;
  color:var(--by-muted);
  font-family:var(--by-font-mono);
  font-size:13px;
  letter-spacing:.03em;
  line-height:1.7;
}
.by-footer__line a{color:var(--by-ice)}
.by-footer__line a:hover{color:var(--by-cyan)}
.by-footer__note{
  margin-top:14px;
  padding-left:12px;
  border-left:3px solid var(--by-ice);
  color:var(--by-ice);
  font-family:var(--by-font-mono);
  font-size:12px;
  letter-spacing:.1em;
}
.by-footer__title{
  padding-bottom:10px;
  border-bottom:1px solid var(--by-line);
  font-family:var(--by-font-mono);
  font-size:12px;
  font-weight:600;
  letter-spacing:.18em;
  text-transform:uppercase;
  color:var(--by-text);
}
.by-footer__list{
  display:grid;
  gap:9px;
  margin-top:14px;
}
.by-footer__list a{
  display:inline-block;
  font-size:14.5px;
  color:var(--by-muted);
  transition:color .18s ease,padding-left .18s var(--by-ease);
}
.by-footer__list a:hover{
  color:var(--by-ice);
  padding-left:6px;
}
.by-footer__bottom{
  display:flex;
  flex-wrap:wrap;
  align-items:center;
  justify-content:space-between;
  gap:10px 24px;
  padding:20px 0 32px;
  border-top:1px solid var(--by-line);
}
.by-footer__legal{
  font-family:var(--by-font-mono);
  font-size:12px;
  letter-spacing:.06em;
  color:var(--by-muted);
}

/* ---------- 12. 返回顶部 ---------- */
.by-to-top{
  position:fixed;
  right:clamp(14px,3vw,34px);
  bottom:clamp(14px,3vw,34px);
  z-index:70;
  display:inline-flex;
  align-items:center;
  gap:8px;
  padding:11px 16px;
  border:3px solid var(--by-line);
  background:var(--by-surface);
  color:var(--by-text);
  font-family:var(--by-font-mono);
  font-size:12px;
  letter-spacing:.12em;
  opacity:0;
  transform:translateY(12px);
  pointer-events:none;
  transition:opacity .3s ease,transform .3s var(--by-ease),
             border-color .2s ease,color .2s ease;
}
.by-to-top[data-visible="true"]{
  opacity:1;
  transform:none;
  pointer-events:auto;
}
.by-to-top:hover{border-color:var(--by-cyan);color:var(--by-cyan)}

/* ---------- 13. 显现动画 ---------- */
.by-js [data-reveal]{opacity:0;transform:translateY(20px)}
[data-reveal]{
  transition:opacity .46s ease,transform .46s var(--by-ease);
}
[data-reveal].is-visible{opacity:1;transform:none}

/* 章节目录（页面阶段使用 [data-toc]） */
[data-toc] a[aria-current="true"]{
  color:var(--by-cyan);
  border-color:var(--by-cyan);
}

/* ---------- 14. 响应式 ---------- */
@media (min-width:1024px){
  .by-brand__sub{display:inline}
  .by-footer__grid{grid-template-columns:1.6fr 1fr 1fr 1fr}
}
@media (min-width:720px){
  .by-footer__grid{grid-template-columns:repeat(2,minmax(0,1fr))}
}
@media (max-width:960px){
  .by-nav-toggle{display:inline-flex}
  .by-nav{
    position:absolute;
    top:100%;
    left:0;
    right:0;
    display:none;
    max-height:calc(100vh - 120px);
    overflow-y:auto;
    background:var(--by-surface);
    border-top:1px solid var(--by-line);
    border-bottom:3px solid var(--by-cyan);
    box-shadow:0 20px 0 rgba(3,7,14,.5);
  }
  .by-nav[data-open="true"]{display:block}
  .by-nav__list{flex-direction:column;align-items:stretch;gap:0;padding:8px 0}
  .by-nav__item{display:block}
  .by-nav__link{
    padding:15px var(--by-gutter);
    border-bottom:1px solid var(--by-line);
    border-left:3px solid transparent;
    font-size:14px;
    letter-spacing:.1em;
  }
  .by-nav__link:hover{background:rgba(127,212,255,.06)}
  .by-nav__link[aria-current="page"]{
    border-bottom-color:var(--by-line);
    border-left-color:var(--by-cyan);
    background:rgba(0,240,224,.07);
  }
  .by-status{display:none}
  .by-header__cta{padding:8px 12px;font-size:11.5px;letter-spacing:.06em}
  .by-section__head{grid-template-columns:auto minmax(0,1fr)}
  .by-section__kicker{display:none}
}
@media (max-width:900px){
  .by-col-3,.by-col-4,.by-col-5,.by-col-6,
  .by-col-7,.by-col-8,.by-col-9,.by-col-12{grid-column:span 12}
}
@media (max-width:760px){
  .by-header__cmd{display:none}
  .by-brand__name{font-size:16px}
  .by-annotation{display:none}
}
@media (max-width:420px){
  .by-brand__name{font-size:15px}
  .by-brand__mark{width:30px;height:30px;font-size:12px}
}

/* ---------- 15. 减弱动效 ---------- */
@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;
  }
  .by-js [data-reveal],
  [data-reveal]{opacity:1 !important;transform:none !important}
  .by-card:hover,
  .by-btn:hover{transform:none}
  .by-header__bar{max-height:64px !important;opacity:1 !important}
}