/* =========================================================
   VPNTd base.css
   Design tokens / reset / layout / typography / buttons /
   site header / hero / site footer / reveal / breakpoints
   All colors reference :root tokens only.
   ========================================================= */

:root{
  /* ---- palette ---- */
  --bg:#0D1311;
  --panel:#131B17;
  --panel2:#1A2420;
  --border:#28382F;
  --accent:#2ECFA6;
  --accent-dark:#1B9E7C;
  --text:#E9F1EC;
  --muted:#94A79D;
  --success:#5BC981;
  --warn:#E3B95E;
  --error:#E06A57;
  --trace:#7A968A;
  --dot:#1E2A24;
  --accent-glow:rgba(46,207,166,.32);
  --accent-glow-soft:rgba(46,207,166,.14);
  --ink-on-accent:#0A1410;
  /* ---- flag fills ---- */
  --fl-red:#C43C3C;
  --fl-blue:#3E5A9E;
  --fl-white:#F2F5F1;
  --fl-green:#3E9E63;
  /* ---- shape & space ---- */
  --radius:12px;
  --radius-s:7px;
  --nav-h:68px;
  --toc-h:52px;
  --gutter:32px;
  --content-w:1360px;
  /* ---- type ---- */
  --font-display:'Inter','Noto Sans SC','PingFang SC','Microsoft YaHei',sans-serif;
  --font-body:'Inter','Noto Sans SC','PingFang SC','Microsoft YaHei',sans-serif;
  --font-mono:'JetBrains Mono','SFMono-Regular',Consolas,'Courier New',monospace;
}

/* ---------------- reset ---------------- */
*,*::before,*::after{margin:0;padding:0;box-sizing:border-box}
html{
  scroll-behavior:smooth;
  scroll-padding-top:calc(var(--nav-h) + 16px);
  -webkit-text-size-adjust:100%;
}
body{
  background:var(--bg);
  color:var(--text);
  font-family:var(--font-body);
  font-size:15px;
  line-height:1.7;
  -webkit-font-smoothing:antialiased;
}
a{text-decoration:none;color:inherit}
ul,ol{list-style:none}
img{max-width:100%;height:auto}
svg{display:inline-block}
[hidden]{display:none!important}
button{font:inherit;color:inherit;background:none;border:none;cursor:pointer}
input,select,textarea{font:inherit;color:inherit}
html.nav-open{overflow:hidden}

/* keyboard focus (a11y baseline) */
a:focus-visible,
button:focus-visible,
summary:focus-visible,
input:focus-visible,
select:focus-visible,
textarea:focus-visible,
[tabindex]:focus-visible{
  outline:2px solid var(--accent);
  outline-offset:2px;
}

/* ---------------- layout ---------------- */
.wrap{
  max-width:var(--content-w);
  margin-inline:auto;
  padding-inline:var(--gutter);
}
.sec{padding-top:72px;padding-bottom:72px}
.sec-tight{padding-top:48px;padding-bottom:48px}
.sec-line{border:none;border-top:1px solid var(--border);margin:0}
.kicker{
  display:inline-block;
  font-family:var(--font-mono);
  font-size:11px;
  letter-spacing:.16em;
  color:var(--accent-dark);
  text-transform:uppercase;
  margin-bottom:12px;
}
.no-break{white-space:nowrap}

/* decorative micro-tilt: NEVER apply to tall content containers;
   always neutralized on narrow screens to avoid overflow */
.tilt{transform:rotate(-.4deg)}
@media (max-width:640px){.tilt{transform:none}}

/* ---------------- typography ---------------- */
h1,h2,h3,h4{
  font-family:var(--font-display);
  font-weight:800;
  letter-spacing:-.012em;
  line-height:1.18;
  text-wrap:balance;
}
h1{font-size:clamp(36px,4.6vw,62px);line-height:1.12;letter-spacing:-.015em}
h2{font-size:clamp(24px,3vw,34px)}
h3{font-size:19px}
h4{font-size:16px}
p{max-width:100%}
.lede{
  font-size:16.5px;
  color:var(--muted);
  line-height:1.75;
  max-width:640px;
}
strong{color:var(--text);font-weight:600}
.kw{
  background:linear-gradient(120deg,var(--accent) 20%,var(--accent-dark) 90%);
  -webkit-background-clip:text;
  background-clip:text;
  -webkit-text-fill-color:transparent;
  color:transparent;
}
code{
  font-family:var(--font-mono);
  font-size:.88em;
  background:var(--panel2);
  border:1px solid var(--border);
  border-radius:4px;
  padding:.1em .4em;
  overflow-wrap:anywhere;   /* long tokens / URLs must never blow 375px */
  word-break:break-word;
}
pre{
  font-family:var(--font-mono);
  font-size:13px;
  line-height:1.6;
  background:var(--panel);
  border:1px solid var(--border);
  border-radius:var(--radius-s);
  padding:16px 18px;
  overflow-x:auto;
  max-width:100%;
  -webkit-overflow-scrolling:touch;
}
pre code{background:none;border:none;padding:0}

/* ---------------- buttons ---------------- */
.btn-primary{
  display:inline-flex;
  align-items:center;
  justify-content:center;
  gap:8px;
  background:linear-gradient(150deg,var(--accent),var(--accent-dark));
  color:var(--ink-on-accent);
  font-size:16px;
  font-weight:700;
  padding:14px 32px;
  border-radius:var(--radius-s);
  box-shadow:0 0 0 1px var(--accent-dark),0 8px 28px var(--accent-glow);
  transition:transform .15s,box-shadow .15s;
  min-height:48px;
}
.btn-primary:hover{
  transform:translateY(-1px);
  box-shadow:0 0 0 1px var(--accent),0 10px 34px var(--accent-glow);
}
.btn-secondary{
  display:inline-flex;
  align-items:center;
  justify-content:center;
  gap:8px;
  font-size:15px;
  font-weight:600;
  color:var(--text);
  border:1px solid var(--border);
  background:var(--panel);
  padding:13px 26px;
  border-radius:var(--radius-s);
  transition:border-color .15s,background-color .15s;
  min-height:48px;
}
.btn-secondary:hover{border-color:var(--accent-dark);background:var(--panel2)}
.btn-ghost{
  display:inline-flex;
  align-items:center;
  justify-content:center;
  gap:8px;
  font-size:14px;
  font-weight:600;
  color:var(--muted);
  border:1px solid var(--border);
  background:none;
  padding:10px 20px;
  border-radius:var(--radius-s);
  transition:color .15s,border-color .15s;
  min-height:44px;
}
.btn-ghost:hover{color:var(--text);border-color:var(--accent-dark)}
.btn-sm{font-size:13.5px;padding:9px 18px;min-height:40px}

/* ---------------- site header ---------------- */
.site-head{
  position:sticky;
  top:0;
  z-index:60;
  height:var(--nav-h);
  border-bottom:1px solid var(--border);
  background:var(--panel);
  display:flex;
  align-items:center;
}
.head-inner{
  width:min(var(--content-w),calc(100% - var(--gutter)*2));
  margin-inline:auto;
  display:flex;
  align-items:center;
  gap:24px;
}
.brand{display:flex;align-items:center;gap:10px;flex:0 0 auto}
.brand-logo{display:block;width:30px;height:30px;flex-shrink:0}
.brand-name{font-weight:800;font-size:17px;letter-spacing:.02em;color:var(--text)}
.main-nav{display:flex;align-items:center;gap:4px;flex:1 1 auto;min-width:0}
.main-nav a{
  display:flex;
  align-items:center;
  gap:6px;
  font-size:13px;
  color:var(--muted);
  padding:8px 10px;
  border-radius:var(--radius-s);
  transition:color .15s,background-color .15s;
  white-space:nowrap;
}
.main-nav a:hover{color:var(--text);background:var(--panel2)}
.main-nav a.is-active{color:var(--text)}
.main-nav a svg{flex:0 0 auto;display:block}
.head-actions{display:flex;align-items:center;gap:10px;flex:0 0 auto}

.lang-wrap{position:relative}
.lang-switch{
  display:inline-flex;
  align-items:center;
  gap:6px;
  font-size:12.5px;
  color:var(--muted);
  padding:8px 10px;
  border-radius:var(--radius-s);
  border:1px solid transparent;
  min-height:36px;
}
.lang-switch:hover{color:var(--text);border-color:var(--border)}
.lang-drop{
  position:absolute;
  top:calc(100% + 8px);
  right:0;
  min-width:150px;
  background:var(--panel2);
  border:1px solid var(--border);
  border-radius:var(--radius-s);
  padding:6px;
  display:none;
  box-shadow:0 14px 36px rgba(0,0,0,.45);
}
.lang-wrap.open .lang-drop{display:block}
.lang-drop a{
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap:10px;
  font-size:13px;
  color:var(--muted);
  padding:9px 12px;
  border-radius:5px;
  min-height:38px;
}
.lang-drop a:hover{color:var(--text);background:var(--panel)}
.lang-drop a.is-cur{color:var(--accent)}
.lang-check{color:var(--accent);font-size:12px;flex-shrink:0}

.btn-login{
  display:inline-flex;
  align-items:center;
  justify-content:center;
  font-size:13px;
  font-weight:600;
  color:var(--text);
  border:1px solid var(--border);
  background:var(--panel2);
  padding:8px 18px;
  border-radius:var(--radius-s);
  transition:border-color .15s;
  min-height:38px;
  white-space:nowrap;
}
.btn-login:hover{border-color:var(--accent-dark)}

.burger{
  display:none;
  flex-direction:column;
  align-items:center;
  justify-content:center;
  gap:4px;
  width:44px;
  height:44px;
  border-radius:var(--radius-s);
}
.burger:hover{background:var(--panel2)}
.burger-bar{
  display:block;
  width:18px;
  height:2px;
  border-radius:2px;
  background:var(--text);
  transition:transform .2s,opacity .2s;
}
html.nav-open .burger-bar:nth-child(1){transform:translateY(6px) rotate(45deg)}
html.nav-open .burger-bar:nth-child(2){opacity:0}
html.nav-open .burger-bar:nth-child(3){transform:translateY(-6px) rotate(-45deg)}

.nav-drawer{display:none}
.nav-veil{display:none}

@media (max-width:960px){
  .main-nav{display:none}
  .burger{display:inline-flex}
  .head-actions{margin-left:auto}
  html.nav-open .nav-veil{
    display:block;
    position:fixed;
    left:0;right:0;
    top:var(--nav-h);bottom:0;
    background:rgba(6,10,8,.62);
    z-index:1;
  }
  html.nav-open .nav-drawer{
    display:block;
    position:fixed;
    top:var(--nav-h);
    left:0;right:0;
    max-height:calc(100dvh - var(--nav-h));
    overflow-y:auto;
    overscroll-behavior:contain;
    background:var(--panel);
    border-bottom:1px solid var(--border);
    z-index:2;
    padding-bottom:16px;
  }
  .nav-drawer a{
    display:flex;
    align-items:center;
    gap:10px;
    min-height:48px;
    padding:12px 20px;
    font-size:14.5px;
    color:var(--text);
    border-bottom:1px solid var(--border);
  }
  .nav-drawer a svg{flex:0 0 auto}
  .nav-drawer a.is-active{color:var(--accent)}
  .nav-drawer .drawer-langs-key{
    display:block;
    font-family:var(--font-mono);
    font-size:10px;
    letter-spacing:.16em;
    color:var(--muted);
    padding:16px 20px 8px;
  }
  .nav-drawer .drawer-langs a{
    color:var(--muted);
    border-bottom:none;
    min-height:44px;
    padding:10px 20px;
  }
  .nav-drawer .drawer-langs a.is-cur{color:var(--accent)}
}

/* ---------------- hero (visual-right, circuit trace board) ---------------- */
.hero{
  min-height:calc(100svh - var(--nav-h) - 60px);
  display:flex;
  align-items:center;
  border-bottom:1px solid var(--border);
  background:
    radial-gradient(900px 480px at 78% 30%,var(--accent-glow-soft),transparent 68%),
    var(--bg);
  overflow-x:clip; /* absolutely-positioned glow decorations can never escape */
}
.hero-inner{
  width:min(var(--content-w),calc(100% - var(--gutter)*2));
  margin-inline:auto;
  display:grid;
  grid-template-columns:minmax(0,560px) minmax(0,620px);
  justify-content:space-between;
  align-items:center;
  gap:56px;
  padding-top:40px;
  padding-bottom:44px;
}
.hero-copy{position:relative;z-index:2}
.hero-visual{position:relative;min-width:0}

.hero-badge{
  display:inline-flex;
  align-items:center;
  gap:8px;
  border:1px solid var(--border);
  background:var(--panel);
  border-radius:999px;
  padding:6px 14px;
  font-size:12.5px;
  color:var(--muted);
}
.hero-badge .dot{
  width:7px;height:7px;border-radius:50%;
  background:var(--success);
  box-shadow:0 0 8px var(--success);
  flex-shrink:0;
}
.hero-badge .mono{font-family:var(--font-mono);font-size:11px;letter-spacing:.08em;color:var(--muted)}

.hero h1{margin:22px 0 26px;font-family:var(--font-display);font-weight:800}
.hero h1 .kw{white-space:nowrap}

.cta-row{display:flex;align-items:center;gap:14px;margin-bottom:24px;flex-wrap:wrap}
.hero-desc{
  font-size:15.5px;
  line-height:1.75;
  color:var(--muted);
  max-width:520px;
  margin-bottom:20px;
}
.hero-desc strong{color:var(--text);font-weight:600}

.trust-row{
  display:flex;
  flex-wrap:wrap;
  align-items:center;
  gap:6px 0;
  font-size:13px;
  color:var(--muted);
  margin-bottom:26px;
}
.trust-row li{display:flex;align-items:center}
.trust-row li + li::before{content:"·";margin:0 10px;color:var(--border)}

.spec-row{
  display:flex;
  align-items:center;
  gap:16px;
  padding-top:14px;
  border-top:1px solid var(--border);
  margin-bottom:12px;
  flex-wrap:wrap;
}
.spec-key{
  font-family:var(--font-mono);
  font-size:10px;
  letter-spacing:.14em;
  color:var(--muted);
  flex:0 0 64px;
}
.platforms{display:flex;align-items:center;gap:18px;flex-wrap:wrap}
.platforms li{display:flex;align-items:center;gap:6px;font-size:12.5px;color:var(--muted)}
.platforms svg{display:block;color:var(--muted);flex-shrink:0}
.flags{display:flex;align-items:center;gap:16px;flex-wrap:wrap}
.flags li{display:flex;align-items:center;gap:7px;font-size:12.5px;color:var(--muted)}
.flags svg{display:block;border-radius:3px;box-shadow:0 0 0 1px var(--border);flex-shrink:0}
.f-red{fill:var(--fl-red)}
.f-white{fill:var(--fl-white)}
.f-blue{fill:var(--fl-blue)}
.f-green{fill:var(--fl-green)}

/* ---- circuit trace board ---- */
.board{
  position:relative;
  background:var(--panel);
  border:1px solid var(--border);
  border-radius:var(--radius);
  box-shadow:0 24px 60px rgba(0,0,0,.4),0 2px 8px rgba(0,0,0,.3);
  overflow:hidden;
}
.board-head{
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap:12px;
  padding:14px 20px;
  border-bottom:1px solid var(--border);
  font-family:var(--font-mono);
  font-size:11px;
  letter-spacing:.1em;
  color:var(--muted);
}
.board-status{display:flex;align-items:center;gap:8px;color:var(--text)}
.board-status .dot{
  width:7px;height:7px;border-radius:50%;
  background:var(--accent);
  box-shadow:0 0 10px var(--accent-glow),0 0 4px var(--accent);
  flex-shrink:0;
}
.board-canvas{
  padding:14px 18px 6px;
  background-image:radial-gradient(var(--dot) 1px,transparent 1px);
  background-size:18px 18px;
}
.board-canvas svg{display:block;width:100%;height:auto}
.board-chips{
  display:flex;
  align-items:center;
  gap:10px;
  padding:14px 20px 18px;
  flex-wrap:wrap;
}
.board-chips .chip-key{
  font-family:var(--font-mono);
  font-size:10px;
  letter-spacing:.14em;
  color:var(--muted);
  margin-right:2px;
}

/* SVG trace styles */
.tr-deco{stroke:var(--border);stroke-width:1.4;fill:none;opacity:.7}
.tr-deco-via{fill:var(--panel2);stroke:var(--border);stroke-width:1.2}
.tr-glow{stroke:var(--accent-dark);stroke-width:6;fill:none;stroke-linejoin:round;opacity:.3;filter:url(#soft)}
.tr-main{
  stroke:var(--trace);
  stroke-width:2;
  fill:none;
  stroke-linejoin:round;
  stroke-linecap:round;
  stroke-dasharray:660;
  stroke-dashoffset:660;
  animation:tracedash 1.7s .4s ease-out forwards;
}
.tr-pad{fill:var(--panel2);stroke:var(--trace);stroke-width:1.6}
.tr-pad-hot{fill:var(--panel2);stroke:var(--accent-dark);stroke-width:1.8}
.tr-pad-ring{fill:none;stroke:var(--accent-dark);stroke-width:1;opacity:.45}
.tr-via-outer{fill:var(--panel2);stroke:var(--trace);stroke-width:1.6}
.tr-via-hole{fill:var(--bg)}
.tr-label{font-family:var(--font-mono);font-size:11px;fill:var(--muted);letter-spacing:.03em}
.tr-label-hot{font-family:var(--font-mono);font-size:11px;fill:var(--text);letter-spacing:.03em}
.tr-corner{font-family:var(--font-mono);font-size:10px;fill:var(--muted);letter-spacing:.12em;opacity:.75}
.pk-halo{fill:var(--accent);opacity:.22}
.pk-core{fill:var(--accent)}
.pulse{opacity:0;animation:packet 6s 2.2s cubic-bezier(.45,.05,.55,.95) infinite}

@keyframes tracedash{to{stroke-dashoffset:0}}
@keyframes packet{
  0%{transform:translate(70px,435px);opacity:0}
  4%{opacity:1}
  14%{transform:translate(150px,388px)}
  18%{transform:translate(138px,366px)}
  28%{transform:translate(205px,340px)}
  42%{transform:translate(285px,292px)}
  46%{transform:translate(272px,270px)}
  56%{transform:translate(335px,243px)}
  72%{transform:translate(430px,188px)}
  76%{transform:translate(418px,166px)}
  93%{transform:translate(520px,110px);opacity:1}
  100%{transform:translate(520px,110px);opacity:0}
}

/* ---------------- site footer ---------------- */
.site-foot{
  background:var(--panel);
  border-top:1px solid var(--border);
}
.foot-grid{
  display:grid;
  grid-template-columns:minmax(230px,1.5fr) minmax(160px,1fr) minmax(160px,1fr) minmax(140px,1fr);
  gap:36px;
  padding-top:52px;
  padding-bottom:44px;
}
.foot-brand .brand{margin-bottom:14px}
.foot-intro{font-size:13px;color:var(--muted);line-height:1.75;max-width:340px}
.foot-col h3{
  font-family:var(--font-mono);
  font-size:10.5px;
  font-weight:600;
  letter-spacing:.16em;
  text-transform:uppercase;
  color:var(--muted);
  margin-bottom:14px;
}
.foot-col li{margin-bottom:2px;min-width:0}
.foot-col a{
  display:inline-flex;
  align-items:center;
  min-height:32px;
  font-size:13px;
  color:var(--muted);
  transition:color .15s;
}
.foot-col a:hover{color:var(--text)}
.foot-col a.is-cur{color:var(--accent)}
.foot-bottom{
  display:flex;
  flex-wrap:wrap;
  align-items:center;
  justify-content:space-between;
  gap:10px 24px;
  border-top:1px solid var(--border);
  padding-top:20px;
  padding-bottom:26px;
}
.foot-copy{font-size:12.5px;color:var(--muted)}
.foot-legal{display:flex;gap:18px;flex-wrap:wrap}
.foot-legal a{font-size:12.5px;color:var(--muted)}
.foot-legal a:hover{color:var(--text)}

/* ---------------- generic cards / panels ---------------- */
.panel{background:var(--panel);border:1px solid var(--border);border-radius:var(--radius)}
.panel-pad{padding:24px}
.card{
  background:var(--panel);
  border:1px solid var(--border);
  border-radius:var(--radius);
  padding:24px;
  transition:border-color .15s,transform .15s;
}
.card:hover{border-color:var(--accent-dark);transform:translateY(-2px)}

/* ---------------- scroll reveal (visibility owned by reveal.js) ---------------- */
.reveal{transition:opacity .6s ease,transform .6s ease}
.reveal.pending{opacity:0;transform:translateY(16px)}
.reveal.shown{opacity:1;transform:none}

/* ---------------- breakpoints ---------------- */
@media (max-width:1180px){
  .hero-inner{grid-template-columns:1fr;gap:40px}
  .hero{min-height:auto}
  h1{font-size:clamp(32px,4.2vw,48px)}
}
@media (max-width:900px){
  /* tablet: fixed min column widths (230/160/160/140 + gaps) exceed a
     768px viewport — collapse to a 2-column grid, brand row spans full width */
  .foot-grid{
    grid-template-columns:minmax(0,1fr) minmax(0,1fr);
    gap:28px 24px;
  }
  .foot-brand{grid-column:1 / -1}
}
@media (max-width:720px){
  :root{--gutter:20px}
  h1{font-size:clamp(28px,7.6vw,38px)}
  .hero-inner{padding-top:32px;padding-bottom:36px}
  .trust-row{font-size:12.5px}
  .spec-row{gap:10px}
  /* footer: fixed min column widths (230/160/160/140 + gaps) exceed a
     390px viewport and force ~420px of horizontal overflow — collapse
     to a 2-column grid with the brand row spanning full width */
  .foot-grid{
    grid-template-columns:minmax(0,1fr) minmax(0,1fr);
    gap:28px 24px;
    padding-top:40px;
    padding-bottom:32px;
  }
  .foot-brand{grid-column:1 / -1}
}
@media (max-width:560px){
  /* narrow header: top-bar language switch lives in the drawer already;
     keep brand + login + burger inside the viewport */
  .lang-wrap{display:none}
  .btn-login{padding:8px 12px;font-size:12.5px}
  .head-inner{gap:12px}
}
@media (max-width:480px){
  :root{--gutter:16px}
  .cta-row .btn-primary,.cta-row .btn-secondary{flex:1 1 auto}
  .foot-grid{gap:24px 18px}
}

/* ---------------- reduced motion ---------------- */
@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  .tr-main{animation:none;stroke-dashoffset:0}
  .pulse{animation:none;opacity:1;transform:translate(520px,110px)}
  .btn-primary,.btn-primary:hover{transform:none}
  .card:hover{transform:none}
  .burger-bar{transition:none}
  .reveal,.reveal.pending{transition:none;opacity:1;transform:none}
}