/* StaySilent 匿声 — design system (contract for all sections)
   Dark-led terminal palette, 1px border modular grid, single signal-cyan accent. */

:root{
  --bg:#0a0a0a;
  --surface:#111111;
  --border:#222222;
  --text:#cccccc;
  --heading:#ffffff;
  --muted:#666666;
  --accent:#3af2c0;
  --accent-dim:rgba(58,242,192,.12);
  --font-mono:ui-monospace,"Cascadia Code","JetBrains Mono",Menlo,Consolas,monospace;
  --font-sans:-apple-system,"PingFang SC","Hiragino Sans GB","Microsoft YaHei","Noto Sans SC",sans-serif;
  --wrap:1200px;
}

*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
body{
  background:var(--bg);
  color:var(--text);
  font-family:var(--font-sans);
  font-size:16px;
  line-height:1.7;
  -webkit-font-smoothing:antialiased;
  text-rendering:optimizeLegibility;
}
::selection{background:var(--accent);color:#000}
a{color:inherit;text-decoration:none}
ul,ol{list-style:none}
img,canvas,svg{display:block;max-width:100%}
button{font:inherit;color:inherit;background:none;border:0;cursor:pointer}

/* ---------- layout primitives ---------- */
.wrap{max-width:var(--wrap);margin:0 auto;padding:0 24px}
.sec{padding:96px 0;border-top:1px solid var(--border)}
.sec-head{max-width:720px;margin-bottom:56px}
.sec-head.center{margin-left:auto;margin-right:auto;text-align:center}

/* ---------- typography ---------- */
.mono{font-family:var(--font-mono)}
.kicker{
  font-family:var(--font-mono);
  font-size:12px;letter-spacing:.18em;text-transform:uppercase;
  color:var(--accent);margin-bottom:16px;
}
.h-display{
  font-size:clamp(40px,6.5vw,76px);
  line-height:1.12;letter-spacing:-0.02em;
  color:var(--heading);font-weight:700;
}
.h-sec{
  font-size:clamp(28px,4vw,44px);
  line-height:1.2;letter-spacing:-0.02em;
  color:var(--heading);font-weight:700;margin-bottom:16px;
}
.lead{font-size:18px;color:var(--text);max-width:56ch}
.small{font-size:13px;color:var(--muted)}
.accent-text{color:var(--accent)}

/* ---------- grids & cells ---------- */
.grid{display:grid;gap:0}
.grid-2{grid-template-columns:repeat(2,1fr)}
.grid-3{grid-template-columns:repeat(3,1fr)}
.grid-4{grid-template-columns:repeat(4,1fr)}
.cell{
  border:1px solid var(--border);
  margin:-1px 0 0 -1px;      /* collapse borders into a true modular grid */
  padding:32px 28px;
  background:var(--bg);
  transition:background .15s ease;
}
.cell:hover{background:var(--surface)}

/* ---------- buttons ---------- */
.btn{display:inline-flex;align-items:center;gap:10px;font-weight:600;transition:all .15s ease}
.btn-primary{
  background:var(--accent);color:#000;
  padding:14px 28px;font-size:15px;
}
.btn-primary:hover{background:#fff}
.btn-text{
  color:var(--heading);padding:14px 0;font-size:15px;
}
.btn-text .arrow{display:inline-block;transition:transform .15s ease}
.btn-text:hover{color:var(--accent)}
.btn-text:hover .arrow{transform:translateX(6px)}

/* ---------- tags & stats ---------- */
.tag{
  font-family:var(--font-mono);font-size:11px;letter-spacing:.12em;text-transform:uppercase;
  border:1px solid var(--border);color:var(--muted);padding:4px 10px;display:inline-block;
}
.stat{padding:24px 0;border-top:1px solid var(--border)}
.stat-num{
  font-family:var(--font-mono);font-size:clamp(28px,3.5vw,40px);
  color:var(--accent);font-weight:600;line-height:1.1;
}
.stat-label{font-size:13px;color:var(--muted);margin-top:6px}

/* ---------- cards ---------- */
.card{border:1px solid var(--border);background:var(--surface);padding:32px 28px}
.divider{height:1px;background:var(--border);margin:24px 0}

/* ---------- nav ---------- */
.nav{
  position:sticky;top:0;z-index:100;
  background:rgba(10,10,10,.8);
  backdrop-filter:blur(12px);-webkit-backdrop-filter:blur(12px);
  border-bottom:1px solid var(--border);
}
.nav-inner{
  max-width:var(--wrap);margin:0 auto;padding:0 24px;
  height:64px;display:flex;align-items:center;justify-content:space-between;gap:24px;
}
.nav-logo{display:flex;align-items:baseline;gap:10px;color:var(--heading);font-weight:700;font-size:17px}
.nav-logo .mono{color:var(--accent);font-size:12px;font-weight:400;letter-spacing:.15em}
.nav-links{display:flex;gap:28px;font-size:14px;color:var(--text)}
.nav-links a{transition:color .15s ease}
.nav-links a:hover{color:var(--accent)}
.nav .btn-primary{padding:9px 20px;font-size:13px}

/* ---------- demo panel (hero) ---------- */
.demo-panel{border:1px solid var(--border);background:var(--surface);position:relative}
.demo-head{
  display:flex;align-items:center;justify-content:space-between;
  padding:14px 20px;border-bottom:1px solid var(--border);
  font-family:var(--font-mono);font-size:12px;color:var(--muted);letter-spacing:.1em;
}
.demo-toggle{
  display:inline-flex;align-items:center;gap:10px;
  font-family:var(--font-mono);font-size:12px;letter-spacing:.1em;
  color:var(--muted);transition:color .15s ease;cursor:pointer;
}
.demo-toggle .sw{
  width:40px;height:22px;border:1px solid var(--muted);position:relative;transition:border-color .15s ease;
}
.demo-toggle .sw::after{
  content:"";position:absolute;top:3px;left:3px;width:14px;height:14px;
  background:var(--muted);transition:all .2s ease;
}
.demo-toggle.on{color:var(--accent)}
.demo-toggle.on .sw{border-color:var(--accent)}
.demo-toggle.on .sw::after{left:21px;background:var(--accent)}
.spectrum-canvas{width:100%;height:280px;pointer-events:none}
.demo-foot{
  display:flex;flex-wrap:wrap;gap:24px;padding:16px 20px;border-top:1px solid var(--border);
}
.readout{font-family:var(--font-mono);font-size:12px;color:var(--muted);letter-spacing:.06em}
.readout b{color:var(--accent);font-weight:600}

/* ---------- compare table ---------- */
.compare-table{width:100%;border-collapse:collapse;font-size:15px}
.compare-table th,.compare-table td{
  border:1px solid var(--border);padding:16px 20px;text-align:left;vertical-align:top;
}
.compare-table thead th{
  font-family:var(--font-mono);font-size:12px;letter-spacing:.12em;text-transform:uppercase;
  color:var(--muted);font-weight:400;background:var(--surface);
}
.compare-table th.col-brand{color:var(--accent);background:var(--accent-dim)}
.compare-table td.col-brand{background:var(--accent-dim);color:var(--heading)}
.compare-table td:first-child{color:var(--muted);font-size:13px}

/* ---------- pricing ---------- */
.price-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:0}
.price-card{
  border:1px solid var(--border);margin:-1px 0 0 -1px;
  padding:40px 32px;display:flex;flex-direction:column;background:var(--bg);
}
.price-card.featured{background:var(--surface);position:relative}
.price-card.featured::before{
  content:"热门";position:absolute;top:-1px;right:24px;
  font-family:var(--font-mono);font-size:11px;letter-spacing:.15em;
  background:var(--accent);color:#000;padding:4px 12px;
}
.price-name{font-family:var(--font-mono);font-size:13px;letter-spacing:.15em;text-transform:uppercase;color:var(--muted);margin-bottom:16px}
.price-card.featured .price-name{color:var(--accent)}
.price{font-size:clamp(36px,4vw,52px);color:var(--heading);font-weight:700;line-height:1;letter-spacing:-0.02em}
.price .mono{font-size:15px;color:var(--muted);font-weight:400}
.price-features{margin:28px 0;flex:1}
.price-features li{
  padding:12px 0;border-top:1px solid var(--border);font-size:14px;display:flex;gap:10px;
}
.price-features li::before{content:"→";color:var(--accent);font-family:var(--font-mono)}

/* ---------- faq ---------- */
.faq-item{border:1px solid var(--border);margin:-1px 0 0 -1px}
.faq-q{
  width:100%;display:flex;justify-content:space-between;align-items:center;gap:16px;
  padding:22px 28px;text-align:left;color:var(--heading);font-size:16px;font-weight:600;
  transition:color .15s ease;
}
.faq-q:hover{color:var(--accent)}
.faq-q .ico{font-family:var(--font-mono);color:var(--accent);font-size:18px;transition:transform .2s ease}
.faq-item.open .faq-q .ico{transform:rotate(45deg)}
.faq-a{max-height:0;overflow:hidden;transition:max-height .25s ease}
.faq-a-inner{padding:0 28px 24px;color:var(--text);font-size:15px;max-width:70ch}

/* ---------- footer ---------- */
.footer{border-top:1px solid var(--border);padding:64px 0 32px;background:var(--bg)}
.footer-grid{display:grid;grid-template-columns:2fr 1fr 1fr;gap:48px;margin-bottom:48px}
.footer h4{font-family:var(--font-mono);font-size:12px;letter-spacing:.15em;text-transform:uppercase;color:var(--muted);margin-bottom:16px;font-weight:400}
.footer li{margin-bottom:10px;font-size:14px}
.footer a:hover{color:var(--accent)}
.footer-bottom{
  border-top:1px solid var(--border);padding-top:24px;
  display:flex;flex-wrap:wrap;gap:16px;justify-content:space-between;
  font-family:var(--font-mono);font-size:12px;color:var(--muted);
}

/* ---------- modal ---------- */
.modal{position:fixed;inset:0;z-index:200;display:none;align-items:center;justify-content:center}
.modal.show{display:flex}
.modal-mask{position:absolute;inset:0;background:rgba(0,0,0,.75);backdrop-filter:blur(4px)}
.modal-card{
  position:relative;background:var(--surface);border:1px solid var(--border);
  width:min(420px,calc(100vw - 48px));padding:36px 32px;
}
.modal-card h3{color:var(--heading);font-size:20px;margin-bottom:8px}
.modal-close{
  position:absolute;top:14px;right:18px;font-family:var(--font-mono);
  color:var(--muted);font-size:18px;line-height:1;
}
.modal-close:hover{color:var(--accent)}
.copy-row{
  display:flex;align-items:center;justify-content:space-between;gap:12px;
  border:1px solid var(--border);padding:12px 16px;margin-top:12px;
  font-family:var(--font-mono);font-size:14px;
}
.copy-btn{color:var(--accent);font-family:var(--font-mono);font-size:12px;letter-spacing:.1em;white-space:nowrap}
.copy-btn:hover{text-decoration:underline}

/* ---------- sticky cta ---------- */
.sticky-cta{
  position:fixed;left:0;right:0;bottom:0;z-index:90;
  background:rgba(10,10,10,.9);backdrop-filter:blur(12px);
  border-top:1px solid var(--border);
  transform:translateY(100%);transition:transform .25s ease;
}
.sticky-cta.show{transform:translateY(0)}
.sticky-cta-inner{
  max-width:var(--wrap);margin:0 auto;padding:12px 24px;
  display:flex;align-items:center;justify-content:space-between;gap:16px;
  font-size:14px;
}
.sticky-cta .btn-primary{padding:10px 22px;font-size:13px}

/* ---------- responsive ---------- */
@media (max-width:960px){
  .grid-4{grid-template-columns:repeat(2,1fr)}
  .grid-3{grid-template-columns:repeat(2,1fr)}
  .price-grid{grid-template-columns:1fr}
  .footer-grid{grid-template-columns:1fr 1fr}
  .nav-links{display:none}
}
@media (max-width:600px){
  .sec{padding:64px 0}
  .grid-4,.grid-3,.grid-2{grid-template-columns:1fr}
  .footer-grid{grid-template-columns:1fr}
  .sticky-cta-inner{font-size:12px}
}