/* ===================================================================
   老头vpn (oldmanvpn.mom) - 超音速战隼与机载平显 HUD 设计系统 (Supersonic Avionics UI)
   排版创新：全幅机载平显 HUD 状态栏 + 驾驶舱分屏 Hero + 对照基准表 + 倒角战术档案卡
   背景创新：战术遥测刻度网格 (+) + 45° 超音速激波流线 + 碳纤维复合材质底色
   =================================================================== */

:root {
  --bg-cockpit: #090c12;
  --bg-avionics: #0e131d;
  --bg-card: rgba(17, 24, 39, 0.78);
  --bg-card-hover: rgba(26, 36, 58, 0.9);

  --hud-yellow: #facc15;
  --hud-amber: #f97316;
  --hud-cyan: #38bdf8;
  --hud-red: #ef4444;
  --hud-green: #22c55e;

  --text-white: #ffffff;
  --text-primary: #f8fafc;
  --text-secondary: #cbd5e1;
  --text-muted: #94a3b8;
  --text-dim: #64748b;

  --border-hud: rgba(250, 204, 21, 0.25);
  --border-hud-bright: #facc15;
  --border-dark: #1e293b;

  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;

  --radius-xs: 2px;
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 16px;

  --shadow-hud: 0 4px 25px rgba(0, 0, 0, 0.7), inset 0 0 0 1px var(--border-hud);
  --shadow-afterburner: 0 0 30px rgba(245, 158, 11, 0.25);
}

*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg-cockpit);
  color: var(--text-primary);
  line-height: 1.75;
  overflow-x: hidden;
  /* Telemetry Grid & Slipstream Background */
  background-image: 
    linear-gradient(rgba(250, 204, 21, 0.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(250, 204, 21, 0.03) 1px, transparent 1px),
    repeating-linear-gradient(45deg, rgba(56, 189, 248, 0.015) 0, rgba(56, 189, 248, 0.015) 2px, transparent 2px, transparent 12px);
  background-size: 48px 48px, 48px 48px, auto;
}

a {
  color: var(--hud-yellow);
  text-decoration: none;
  transition: all 0.2s ease;
}

a:hover {
  color: #fff;
}

/* Avionics Telemetry Status Bar Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(9, 12, 18, 0.94);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border-hud);
}

.header-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0.75rem 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.brand-telemetry {
  display: flex;
  align-items: center;
  gap: 0.8rem;
}

.brand-name {
  font-size: 1.35rem;
  font-weight: 900;
  color: #fff;
  letter-spacing: 0.04em;
}

.brand-name span {
  color: var(--hud-yellow);
}

.telemetry-chip {
  font-family: var(--font-mono);
  font-size: 0.74rem;
  color: var(--hud-yellow);
  background: rgba(250, 204, 21, 0.1);
  padding: 0.2rem 0.55rem;
  border-radius: var(--radius-xs);
  border: 1px solid var(--border-hud);
}

.main-nav {
  display: flex;
  align-items: center;
  gap: 1.4rem;
}

.nav-link {
  font-size: 0.92rem;
  font-weight: 600;
  color: var(--text-secondary);
  padding: 0.35rem 0.65rem;
  transition: all 0.2s ease;
  letter-spacing: 0.02em;
}

.nav-link:hover, .nav-link.active {
  color: var(--hud-yellow);
}

.btn-header-cta {
  background: linear-gradient(135deg, var(--hud-yellow) 0%, var(--hud-amber) 100%);
  color: #090c12 !important;
  font-weight: 900;
  font-size: 0.86rem;
  padding: 0.45rem 1.25rem;
  clip-path: polygon(8px 0, 100% 0, 100% calc(100% - 8px), calc(100% - 8px) 100%, 0 100%, 0 8px);
  box-shadow: 0 0 16px rgba(250, 204, 21, 0.35);
  transition: all 0.25s ease;
}

.btn-header-cta:hover {
  box-shadow: 0 0 25px rgba(250, 204, 21, 0.55);
}

/* Page Layout */
.page-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 2rem 1.5rem 5rem;
  position: relative;
  z-index: 1;
}

/* Full-width Telemetry Bar above Hero */
.hud-telemetry-banner {
  background: rgba(14, 19, 29, 0.9);
  border: 1px solid var(--border-hud);
  padding: 0.6rem 1.25rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--text-muted);
  margin-bottom: 2.5rem;
  border-radius: var(--radius-sm);
}

.telemetry-live-stat strong {
  color: var(--hud-yellow);
}

/* INNOVATIVE LAYOUT 1: Cockpit Asymmetric Split Hero */
.hero-cockpit-split {
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: 2.5rem;
  align-items: center;
  margin-bottom: 5rem;
}

.hero-left-telemetry {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
}

.hero-badge-stencil {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--hud-yellow);
  background: rgba(250, 204, 21, 0.08);
  border-left: 3px solid var(--hud-yellow);
  padding: 0.35rem 0.9rem;
  margin-bottom: 1.4rem;
  letter-spacing: 0.06em;
}

.hero-title {
  font-size: clamp(2.2rem, 4.2vw, 3.4rem);
  font-weight: 900;
  line-height: 1.2;
  color: #fff;
  margin-bottom: 1.25rem;
  letter-spacing: -0.01em;
}

.hero-title-yellow {
  color: var(--hud-yellow);
  background: linear-gradient(135deg, var(--hud-yellow) 0%, var(--hud-amber) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  display: inline-block;
}

.hero-lead-text {
  font-size: 1.1rem;
  color: var(--text-secondary);
  line-height: 1.8;
  margin-bottom: 2.2rem;
  max-width: 600px;
}

.hero-actions-row {
  display: flex;
  align-items: center;
  gap: 1.2rem;
  flex-wrap: wrap;
  margin-bottom: 2.2rem;
}

.btn-primary-action {
  background: linear-gradient(135deg, var(--hud-yellow) 0%, var(--hud-amber) 100%);
  color: #090c12 !important;
  font-size: 1.05rem;
  font-weight: 900;
  padding: 0.85rem 2.2rem;
  clip-path: polygon(10px 0, 100% 0, 100% calc(100% - 10px), calc(100% - 10px) 100%, 0 100%, 0 10px);
  box-shadow: var(--shadow-afterburner);
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  transition: all 0.25s ease;
}

.btn-primary-action:hover {
  box-shadow: 0 0 35px rgba(250, 204, 21, 0.6);
  transform: translateY(-2px);
}

.btn-secondary-action {
  background: rgba(14, 19, 29, 0.8);
  color: var(--text-secondary) !important;
  border: 1px solid var(--border-hud);
  font-size: 1.05rem;
  font-weight: 700;
  padding: 0.85rem 1.8rem;
  clip-path: polygon(10px 0, 100% 0, 100% calc(100% - 10px), calc(100% - 10px) 100%, 0 100%, 0 10px);
  transition: all 0.2s ease;
}

.btn-secondary-action:hover {
  border-color: var(--hud-yellow);
  color: #fff !important;
}

/* Hero Right: Supersonic Vector Flight Angle Visualizer */
.cockpit-vector-card {
  background: var(--bg-avionics);
  border: 1px solid var(--border-hud);
  border-radius: var(--radius-md);
  padding: 1.8rem;
  box-shadow: var(--shadow-hud);
  position: relative;
}

.vector-radar-hud {
  background: #06080d;
  border: 1px solid var(--border-dark);
  border-radius: var(--radius-sm);
  padding: 1.5rem;
  font-family: var(--font-mono);
  font-size: 0.86rem;
}

.radar-target-reticle {
  height: 140px;
  border: 1px dashed rgba(250, 204, 21, 0.4);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  margin: 1rem 0;
}

.reticle-core-dot {
  width: 12px;
  height: 12px;
  background: var(--hud-yellow);
  border-radius: 50%;
  box-shadow: 0 0 16px #facc15;
}

.reticle-speed-readout {
  position: absolute;
  bottom: 12px;
  font-size: 0.78rem;
  color: var(--hud-cyan);
}

/* INNOVATIVE LAYOUT 2: Side-by-Side Avionics Benchmark Table */
.benchmark-section {
  margin-bottom: 5rem;
}

.section-header-hud {
  text-align: center;
  margin-bottom: 2.5rem;
}

.section-stencil-tag {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--hud-yellow);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  margin-bottom: 0.5rem;
  display: inline-block;
}

.section-h2-title {
  font-size: 2.1rem;
  font-weight: 900;
  color: #fff;
  letter-spacing: -0.01em;
}

.benchmark-table-card {
  background: var(--bg-avionics);
  border: 1px solid var(--border-hud);
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: var(--shadow-hud);
}

.benchmark-grid-row {
  display: grid;
  grid-template-columns: 1.4fr 1fr 1fr;
  padding: 1.1rem 1.5rem;
  border-bottom: 1px solid var(--border-dark);
  align-items: center;
  font-size: 0.95rem;
}

.benchmark-grid-row.head {
  background: #090c12;
  font-family: var(--font-mono);
  font-weight: 800;
  text-transform: uppercase;
  font-size: 0.82rem;
  color: var(--text-muted);
}

.benchmark-grid-row.head .col-mach5 {
  color: var(--hud-yellow);
}

.benchmark-grid-row:last-child {
  border-bottom: none;
}

.benchmark-grid-row:hover:not(.head) {
  background: rgba(250, 204, 21, 0.04);
}

.col-metric-name {
  font-weight: 600;
  color: #fff;
}

.col-mach1 {
  color: var(--hud-red);
  font-family: var(--font-mono);
}

.col-mach5 {
  color: var(--hud-yellow);
  font-family: var(--font-mono);
  font-weight: 700;
}

/* INNOVATIVE LAYOUT 3: Thunder Vector Flight Latency Calculator */
.calculator-tool-box {
  background: var(--bg-avionics);
  border: 1px solid var(--border-hud);
  border-radius: var(--radius-md);
  padding: 2.5rem;
  margin-bottom: 5rem;
  box-shadow: var(--shadow-hud);
}

.calc-controls-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1.5rem;
  margin-bottom: 2rem;
}

.control-hud-group label {
  display: block;
  font-size: 0.86rem;
  font-weight: 700;
  color: var(--text-secondary);
  margin-bottom: 0.5rem;
  font-family: var(--font-mono);
}

.control-hud-group select {
  width: 100%;
  padding: 0.7rem 0.9rem;
  background: var(--bg-cockpit);
  border: 1px solid var(--border-dark);
  border-radius: var(--radius-sm);
  color: #fff;
  font-size: 0.95rem;
  outline: none;
}

.control-hud-group select:focus {
  border-color: var(--hud-yellow);
  box-shadow: 0 0 10px rgba(250, 204, 21, 0.3);
}

.btn-trigger-calc {
  width: 100%;
  padding: 0.75rem;
  background: linear-gradient(135deg, var(--hud-yellow) 0%, var(--hud-amber) 100%);
  color: #090c12;
  font-weight: 900;
  border: none;
  clip-path: polygon(8px 0, 100% 0, 100% calc(100% - 8px), calc(100% - 8px) 100%, 0 100%, 0 8px);
  cursor: pointer;
  font-size: 1rem;
  margin-top: 1.5rem;
  transition: all 0.2s ease;
}

.btn-trigger-calc:hover {
  box-shadow: 0 0 20px rgba(250, 204, 21, 0.5);
}

.calc-screen-panel {
  background: #05070c;
  border: 1px solid var(--border-dark);
  border-radius: var(--radius-sm);
  padding: 1.5rem;
  font-family: var(--font-mono);
  font-size: 0.88rem;
  line-height: 1.65;
}

.calc-telemetry-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 1.2rem;
  margin-bottom: 1.2rem;
  padding-bottom: 1.2rem;
  border-bottom: 1px solid var(--border-dark);
}

.calc-item-lbl {
  font-size: 0.75rem;
  color: var(--text-dim);
  text-transform: uppercase;
}

.calc-item-val {
  font-size: 1.4rem;
  font-weight: 900;
  color: var(--hud-yellow);
}

/* INNOVATIVE LAYOUT 4: Chamfered Tactical Dossier Cards */
.dossier-grid-section {
  margin-bottom: 5rem;
}

.tactical-cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
  gap: 1.8rem;
}

.tactical-dossier-card {
  background: var(--bg-card);
  border: 1px solid var(--border-hud);
  clip-path: polygon(0 0, calc(100% - 16px) 0, 100% 16px, 100% 100%, 0 100%);
  padding: 2rem;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  box-shadow: var(--shadow-hud);
  transition: all 0.25s ease;
  position: relative;
}

.tactical-dossier-card:hover {
  border-color: var(--hud-yellow);
  transform: translateY(-3px);
  background: var(--bg-card-hover);
}

.card-stencil-stamp {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  color: var(--hud-amber);
  margin-bottom: 0.6rem;
  letter-spacing: 0.08em;
}

.dossier-title-link {
  font-size: 1.18rem;
  font-weight: 800;
  color: #fff;
  line-height: 1.45;
  margin-bottom: 0.6rem;
  display: block;
}

.dossier-title-link:hover {
  color: var(--hud-yellow);
}

.dossier-summary {
  font-size: 0.92rem;
  color: var(--text-muted);
  line-height: 1.65;
  margin-bottom: 1.25rem;
}

.dossier-meta-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 0.82rem;
  color: var(--text-dim);
  border-top: 1px solid var(--border-dark);
  padding-top: 0.85rem;
  font-family: var(--font-mono);
}

/* INNOVATIVE LAYOUT 5: Avionics Flight Checklist FAQ */
.checklist-faq-container {
  display: flex;
  flex-direction: column;
  gap: 1.2rem;
  max-width: 900px;
  margin: 0 auto 5rem;
}

.checklist-faq-item {
  background: var(--bg-avionics);
  border: 1px solid var(--border-hud);
  border-radius: var(--radius-sm);
  padding: 1.6rem;
  box-shadow: var(--shadow-hud);
}

.checklist-faq-q {
  font-size: 1.1rem;
  font-weight: 800;
  color: #fff;
  margin-bottom: 0.7rem;
  display: flex;
  align-items: center;
  gap: 0.7rem;
}

.checklist-indicator {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--hud-yellow);
  background: rgba(250, 204, 21, 0.1);
  padding: 0.15rem 0.5rem;
  border-radius: var(--radius-xs);
  border: 1px solid var(--border-hud);
}

.checklist-faq-a {
  font-size: 0.95rem;
  color: var(--text-muted);
  line-height: 1.7;
}

/* Mach Callout */
.mach-callout-banner {
  background: linear-gradient(135deg, rgba(250, 204, 21, 0.1) 0%, rgba(249, 115, 22, 0.05) 100%);
  border: 1px solid var(--hud-yellow);
  border-radius: var(--radius-md);
  padding: 2.5rem;
  text-align: center;
  box-shadow: var(--shadow-afterburner);
  margin-bottom: 3rem;
}

.mach-callout-banner h3 {
  font-size: 1.6rem;
  font-weight: 900;
  color: #fff;
  margin-bottom: 0.6rem;
}

.mach-callout-banner p {
  font-size: 1rem;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto 1.5rem;
}

/* Legal & In-depth Content Card */
.legal-card, .article-content-card {
  background: var(--bg-avionics);
  border: 1px solid var(--border-hud);
  border-radius: var(--radius-md);
  padding: 2.8rem 2.2rem;
  box-shadow: var(--shadow-hud);
  margin-bottom: 2.5rem;
}

.page-title {
  font-size: 2.2rem;
  font-weight: 900;
  color: #fff;
  line-height: 1.3;
  margin-bottom: 0.8rem;
  letter-spacing: -0.01em;
}

.update-time {
  font-size: 0.88rem;
  color: var(--text-dim);
  margin-bottom: 2rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border-dark);
  font-family: var(--font-mono);
}

.content-body h2 {
  font-size: 1.5rem;
  font-weight: 800;
  color: #fff;
  margin: 2rem 0 1rem;
  padding-bottom: 0.4rem;
  border-bottom: 2px solid var(--border-hud);
}

.content-body h3 {
  font-size: 1.2rem;
  font-weight: 800;
  color: var(--hud-yellow);
  margin: 1.5rem 0 0.75rem;
}

.content-body p {
  font-size: 1.02rem;
  color: var(--text-secondary);
  line-height: 1.8;
  margin-bottom: 1.2rem;
}

.content-body ul, .content-body ol {
  margin: 0.8rem 0 1.4rem 1.6rem;
  color: var(--text-secondary);
  line-height: 1.75;
}

.content-body li {
  margin-bottom: 0.45rem;
}

.content-body blockquote {
  border-left: 4px solid var(--hud-yellow);
  background: rgba(250, 204, 21, 0.06);
  padding: 1rem 1.25rem;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  margin: 1.5rem 0;
  font-size: 0.98rem;
  color: var(--text-secondary);
}

.data-table-wrapper {
  overflow-x: auto;
  margin: 1.6rem 0;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-dark);
}

.data-table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
  font-size: 0.92rem;
}

.data-table th {
  background: #090c12;
  color: #fff;
  padding: 0.85rem 1rem;
  font-weight: 800;
  border-bottom: 1px solid var(--border-dark);
  font-family: var(--font-mono);
}

.data-table td {
  padding: 0.85rem 1rem;
  border-bottom: 1px solid var(--border-dark);
  color: var(--text-secondary);
}

.data-table tr:last-child td {
  border-bottom: none;
}

.data-table tr:hover td {
  background: rgba(250, 204, 21, 0.04);
}

.code-box {
  background: #05070c;
  border: 1px solid var(--border-dark);
  color: var(--hud-yellow);
  padding: 1.25rem;
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
  font-size: 0.88rem;
  line-height: 1.6;
  overflow-x: auto;
  margin: 1.4rem 0;
}

/* Footer */
.site-footer {
  background: #05070c;
  border-top: 1px solid var(--border-dark);
  padding: 3.5rem 1.5rem 2rem;
  margin-top: 4rem;
  position: relative;
  z-index: 1;
}

.footer-container {
  max-width: 1200px;
  margin: 0 auto;
}

.footer-top {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 2.5rem;
  margin-bottom: 2.5rem;
}

.footer-brand p {
  font-size: 0.92rem;
  color: var(--text-dim);
  margin-top: 0.8rem;
  line-height: 1.6;
  max-width: 320px;
}

.footer-col h4 {
  font-size: 0.95rem;
  font-weight: 800;
  color: #fff;
  margin-bottom: 1rem;
  font-family: var(--font-mono);
}

.footer-links {
  list-style: none;
}

.footer-links li {
  margin-bottom: 0.5rem;
}

.footer-links a {
  font-size: 0.88rem;
  color: var(--text-dim);
  transition: color 0.2s;
}

.footer-links a:hover {
  color: var(--hud-yellow);
}

.footer-bottom {
  border-top: 1px solid var(--border-dark);
  padding-top: 1.8rem;
  font-size: 0.82rem;
  color: var(--text-dim);
  display: flex;
  flex-direction: column;
  gap: 0.8rem;
}

.footer-disclosure {
  line-height: 1.6;
}

/* Responsive */
@media (max-width: 960px) {
  .hero-cockpit-split {
    grid-template-columns: 1fr;
    gap: 2rem;
  }
  .hud-telemetry-banner {
    flex-direction: column;
    gap: 0.5rem;
    align-items: flex-start;
  }
  .footer-top {
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 640px) {
  .header-container {
    padding: 0.75rem 1rem;
  }
  .telemetry-chip {
    display: none;
  }
  .main-nav .nav-link {
    display: none;
  }
  .benchmark-grid-row {
    grid-template-columns: 1fr 1fr;
  }
  .benchmark-grid-row .col-mach1 {
    display: none;
  }
  .footer-top {
    grid-template-columns: 1fr;
  }
  .legal-card, .article-content-card {
    padding: 1.8rem 1.2rem;
  }
}