/* ============================================================
   39VPN · base.css
   设计令牌 / reset / 排版 / 按钮 / 头部导航 / 页脚 / reveal
   ============================================================ */

:root{
  /* 色彩令牌 */
  --bg:#FFFFFF;
  --bg-panel:#F4F7FE;
  --bg-deep:#0C1B3A;
  --border:#E3E9F4;
  --border-strong:#C9D4E8;
  --accent:#2E5BFF;
  --accent-dark:#1E3FD8;
  --accent-soft:rgba(46,91,255,.09);
  --text:#101828;
  --muted:#5B6577;
  --ok:#12B76A;
  --warn:#F79009;
  --err:#E5484D;
  --gold:#FFAA1E;
  --pink:#F03D8A;
  /* 暗区文字 */
  --deep-text:#EAF0FF;
  --deep-muted:#9FB0D6;
  --deep-line:rgba(159,176,214,.16);
  /* 旗帜专用色(不参与主题切换) */
  --f-blue:#23408E;
  --f-red:#D0342C;
  --f-green:#1E9E4A;
  --f-white:#FFFFFF;
  /* 纹理与光晕 */
  --grid-line:rgba(46,91,255,.06);
  --grid-line-dark:rgba(159,176,214,.08);
  --glow-gold:rgba(255,170,30,.24);
  --glow-blue:rgba(46,91,255,.20);
  /* 投影 */
  --shadow-win:0 34px 70px -22px rgba(12,27,58,.20),0 14px 30px -14px rgba(12,27,58,.13),0 2px 6px rgba(12,27,58,.05);
  --shadow-btn:0 10px 22px -10px rgba(46,91,255,.55);
  --shadow-card:0 14px 34px -18px rgba(12,27,58,.16);
  /* 圆角 */
  --radius-md:12px;
  --radius-lg:16px;
  --radius-xl:22px;
  --radius-pill:999px;
  /* 栅格 */
  --gutter:24px;
  /* 字体 */
  --font-display:'Inter','Noto Sans SC','PingFang SC','Microsoft YaHei','Hiragino Sans','Malgun Gothic',sans-serif;
  --font-body:'Inter','Noto Sans SC','PingFang SC','Microsoft YaHei','Hiragino Sans','Malgun Gothic',sans-serif;
  --font-mono:'JetBrains Mono','SFMono-Regular',Consolas,'Liberation Mono',Menlo,monospace;
}

/* ============ reset ============ */
*,*::before,*::after{margin:0;padding:0;box-sizing:border-box}
html{scroll-behavior:smooth;scroll-padding-top:80px;-webkit-text-size-adjust:100%}
html.nav-open{overflow:hidden}
body{background:var(--bg);color:var(--text);font-family:var(--font-body);font-size:15px;line-height:1.7;-webkit-font-smoothing:antialiased;overflow-x:clip}
a{text-decoration:none;color:inherit}
ul,ol{list-style:none}
img,svg,video{max-width:100%}
button{font-family:inherit}
::selection{background:var(--accent-soft);color:var(--accent-dark)}

/* 键盘焦点可见(可访问性硬性) */
a:focus-visible,button:focus-visible,summary:focus-visible,input:focus-visible,[tabindex]:focus-visible{
  outline:2px solid var(--accent);
  outline-offset:2px;
}

/* ============ 布局工具 ============ */
.wrap{max-width:1160px;margin:0 auto;padding-inline:var(--gutter)}
.wrap-wide{max-width:1360px;margin:0 auto;padding-inline:var(--gutter)}
.sec{padding-top:84px;padding-bottom:84px}
.sec-tight{padding-top:56px;padding-bottom:56px}
.clip-x{overflow-x:clip}
.minw0{min-width:0}
.no-break{white-space:nowrap}
.svg-defs{position:absolute;width:0;height:0;overflow:hidden}
.center{text-align:center}

/* 区块节奏类只声明纵向,禁止 padding 简写清零左右留白 */

/* ============ 排版 ============ */
h1,h2,h3,h4,h5{font-family:var(--font-display);color:var(--text);letter-spacing:-.015em;text-wrap:balance;overflow-wrap:break-word}
h1{font-size:clamp(32px,4.4vw,58px);font-weight:900;line-height:1.14}
h2{font-size:clamp(26px,3.2vw,40px);font-weight:800;line-height:1.2}
h3{font-size:clamp(19px,2vw,24px);font-weight:800;line-height:1.3}
h4{font-size:16px;font-weight:700;line-height:1.4}
p{overflow-wrap:break-word}
strong{font-weight:700;color:var(--text)}
small{font-size:12.5px}
.muted{color:var(--muted)}
.mono{font-family:var(--font-mono)}

/* 行内代码:超长订阅 URL / 文件名防破版(窄屏惯犯①) */
code{font-family:var(--font-mono);font-size:.9em;background:var(--bg-panel);border:1px solid var(--border);border-radius:6px;padding:.12em .38em;overflow-wrap:anywhere;word-break:break-word}
pre{overflow-x:auto;max-width:100%;-webkit-overflow-scrolling:touch;background:var(--bg-panel);border:1px solid var(--border);border-radius:var(--radius-lg);padding:16px 18px}
pre code{display:block;background:transparent;border:none;padding:0;white-space:pre;overflow-wrap:normal;word-break:normal}

/* ============ 按钮 ============ */
.btn-main{display:inline-flex;align-items:center;justify-content:center;gap:8px;min-height:48px;padding:13px 34px;border-radius:var(--radius-pill);background:var(--accent);color:var(--bg);font-size:15.5px;font-weight:700;box-shadow:var(--shadow-btn);transition:background .15s,transform .15s}
.btn-main:hover{background:var(--accent-dark);transform:translateY(-1px)}
.btn-main svg{display:block;flex-shrink:0}
.btn-sub{display:inline-flex;align-items:center;justify-content:center;gap:8px;min-height:48px;padding:13px 30px;border-radius:var(--radius-pill);border:1.5px solid var(--border-strong);color:var(--text);font-size:15.5px;font-weight:600;background:transparent;transition:border-color .15s,color .15s}
.btn-sub:hover{border-color:var(--accent);color:var(--accent)}
.btn-login{display:inline-flex;align-items:center;justify-content:center;min-height:38px;padding:8px 20px;border:1.5px solid var(--accent);border-radius:var(--radius-pill);color:var(--accent);font-size:13.5px;font-weight:600;background:transparent;transition:background .15s,color .15s;flex-shrink:0}
.btn-login:hover{background:var(--accent);color:var(--bg)}

/* ============ 顶部导航(underline-tabs) ============ */
.topbar{position:sticky;top:0;z-index:30;border-bottom:1px solid var(--border);background:var(--bg)}
.topbar-inner{max-width:1360px;margin:0 auto;padding:0 var(--gutter);height:64px;display:flex;align-items:center;gap:22px}
.brand{display:flex;align-items:center;gap:9px;font-family:var(--font-display);font-weight:800;font-size:18px;letter-spacing:-.01em;color:var(--text);flex-shrink:0}
.brand img{display:block;width:30px;height:30px;flex-shrink:0}
.nav-tabs{display:flex;align-items:center;gap:4px;margin-left:6px;flex:1}
.nav-tabs a{position:relative;display:block;padding:21px 10px;font-size:13.5px;color:var(--muted);font-weight:500;transition:color .15s}
.nav-tabs a:hover{color:var(--text)}
.nav-tabs a.on{color:var(--accent);font-weight:600}
.nav-tabs a.on::after{content:"";position:absolute;left:8px;right:8px;bottom:-1px;height:3px;border-radius:2px 2px 0 0;background:var(--accent)}
.nav-tabs a:not(.on)::after{content:"";position:absolute;left:50%;right:50%;bottom:-1px;height:3px;border-radius:2px 2px 0 0;background:var(--border-strong);transition:left .18s,right .18s}
.nav-tabs a:not(.on):hover::after{left:8px;right:8px}

.nav-side{display:flex;align-items:center;gap:14px;flex-shrink:0}

/* 语言切换 */
.lang-switch{position:relative}
.lang-btn{display:inline-flex;align-items:center;justify-content:center;gap:6px;min-height:36px;min-width:44px;padding:6px 12px;border:1px solid var(--border);border-radius:var(--radius-pill);background:var(--bg);color:var(--muted);font-size:13px;font-weight:500;cursor:pointer;transition:color .15s,border-color .15s}
.lang-btn:hover{color:var(--text);border-color:var(--border-strong)}
.lang-btn svg{display:block;flex-shrink:0}
.lang-menu{position:absolute;right:0;top:calc(100% + 8px);min-width:150px;background:var(--bg);border:1px solid var(--border);border-radius:var(--radius-lg);box-shadow:var(--shadow-card);padding:6px;z-index:40}
.lang-menu a{display:flex;align-items:center;min-height:38px;padding:8px 12px;border-radius:var(--radius-md);font-size:13.5px;color:var(--text)}
.lang-menu a:hover{background:var(--bg-panel)}
.lang-menu a.cur{color:var(--accent);font-weight:700}

/* 汉堡按钮 */
.nav-burger{display:none;min-width:44px;min-height:44px;margin-right:-8px;border:none;background:transparent;cursor:pointer;flex-direction:column;justify-content:center;align-items:center;gap:5px;flex-shrink:0}
.nav-burger span{display:block;width:20px;height:2px;border-radius:2px;background:var(--text);transition:transform .2s,opacity .2s}
html.nav-open .nav-burger span:nth-child(1){transform:translateY(7px) rotate(45deg)}
html.nav-open .nav-burger span:nth-child(2){opacity:0}
html.nav-open .nav-burger span:nth-child(3){transform:translateY(-7px) rotate(-45deg)}

/* 移动抽屉:实色背景、整行可点 */
.nav-drawer{display:none;position:fixed;top:64px;left:0;right:0;bottom:0;z-index:70;background:var(--bg);max-height:calc(100dvh - 64px);overflow-y:auto;overscroll-behavior:contain;padding:8px var(--gutter) 36px;border-top:1px solid var(--border)}
html.nav-open .nav-drawer{display:block}
.nav-drawer > a{display:block;min-height:48px;padding:14px 4px;border-bottom:1px solid var(--border);font-size:15px;font-weight:500;color:var(--text)}
.nav-drawer > a.on{color:var(--accent);font-weight:700}
.drawer-lang-label{padding:20px 4px 8px;font-size:11px;font-weight:700;letter-spacing:.12em;text-transform:uppercase;color:var(--muted)}
.nav-drawer .drawer-lang a{display:block;min-height:44px;padding:12px 4px;border-bottom:1px solid var(--border);font-size:14.5px;color:var(--muted)}
.nav-drawer .drawer-lang a.cur{color:var(--accent);font-weight:700}

.nav-veil{display:none;position:fixed;top:64px;left:0;right:0;bottom:0;z-index:60;background:rgba(12,27,58,.32)}
html.nav-open .nav-veil{display:block}

/* ============ 页脚(暗区) ============ */
.footer{position:relative;background:var(--bg-deep);color:var(--deep-muted);overflow-x:clip}
.footer::before{content:"";position:absolute;inset:0;background-image:linear-gradient(var(--grid-line-dark) 1px,transparent 1px),linear-gradient(90deg,var(--grid-line-dark) 1px,transparent 1px);background-size:44px 44px;pointer-events:none}
.footer-inner{position:relative;max-width:1360px;margin:0 auto;padding:58px var(--gutter) 38px;display:grid;grid-template-columns:1.35fr .9fr 1fr .8fr;gap:36px}
.footer-inner > *{min-width:0}
.footer-brand .brand{color:var(--deep-text)}
.footer-intro{margin-top:14px;font-size:13.5px;line-height:1.75;max-width:320px}
.footer-title{font-family:var(--font-display);font-size:12px;font-weight:700;letter-spacing:.14em;text-transform:uppercase;color:var(--deep-text);margin:0 0 14px}
.footer-col a{display:inline-flex;align-items:center;gap:7px;padding:5px 0;font-size:13.5px;color:var(--deep-muted);transition:color .15s}
.footer-col a:hover{color:var(--deep-text)}
.footer-hot{display:flex;flex-wrap:wrap;gap:8px}
.footer-hot a{display:inline-flex;align-items:center;max-height:32px;padding:6px 12px;border:1px solid var(--deep-line);border-radius:var(--radius-pill);font-size:12.5px;color:var(--deep-muted);transition:color .15s,border-color .15s}
.footer-hot a:hover{color:var(--deep-text);border-color:var(--deep-muted)}
.footer-legal{position:relative;border-top:1px solid var(--deep-line)}
.footer-legal-inner{position:relative;max-width:1360px;margin:0 auto;padding:18px var(--gutter);display:flex;flex-wrap:wrap;align-items:center;gap:8px 22px;font-size:12.5px}
.footer-legal a{color:var(--deep-muted);transition:color .15s}
.footer-legal a:hover{color:var(--deep-text)}
.footer-copy{margin-left:auto;color:var(--deep-muted)}

/* ============ reveal 滚动淡入 ============ */
/* 默认可见;隐藏态由 .pending 单独承担(reveal.js 同步分拣) */
.reveal{transition:opacity .55s ease,transform .55s ease}
.reveal.pending{opacity:0;transform:translateY(16px)}
.reveal.shown{opacity:1;transform:none}
@media (prefers-reduced-motion:reduce){
  .reveal,.reveal.pending,.reveal.shown{transition:none;opacity:1;transform:none}
}

/* ============ 响应式 ============ */
@media (max-width:1200px){
  .nav-tabs a{padding:21px 6px;font-size:12.5px}
}
@media (max-width:1024px){
  .nav-tabs{display:none}
  .nav-burger{display:flex}
  .nav-side{margin-left:auto}
  .topbar-inner{gap:12px}
}
@media (max-width:768px){
  .sec{padding-top:56px;padding-bottom:56px}
  .footer-inner{grid-template-columns:1fr 1fr;gap:28px}
}
@media (max-width:640px){
  /* 装饰性微倾斜在窄屏一律取消(窄屏惯犯②) */
  .tilt{transform:none}
  .btn-main,.btn-sub{width:100%;max-width:340px}
  /* 窄屏顶栏:收紧间距与按钮内衬,防止 375px 横向溢出 */
  .topbar-inner{gap:10px}
  .nav-side{gap:10px}
  .lang-btn{padding:6px 8px}
  .btn-login{padding:8px 12px}
}
@media (max-width:560px){
  .footer-inner{grid-template-columns:1fr;gap:26px}
  .footer-copy{margin-left:0;width:100%}
}