/* ==========================================================================
   CyberGuard Landing Page - Design System & Modern Light Theme (v2.1)
   ========================================================================== */

:root {
  /* Color Palette - Vibrant & Premium Light Theme */
  --color-bg: #f8fafc;
  --color-surface: #ffffff;
  --color-surface-hover: #f1f5f9;
  --color-surface-translucent: rgba(255, 255, 255, 0.85);
  
  --color-text: #0f172a;
  --color-text-muted: #475569;
  --color-text-light: #64748b;
  
  --color-accent: #2563eb;
  --color-accent-hover: #1d4ed8;
  --color-accent-light: #eff6ff;
  --color-accent-border: #bfdbfe;
  
  --color-success: #10b981;
  --color-success-bg: #ecfdf5;
  --color-warning: #f59e0b;
  --color-danger: #ef4444;

  --color-border: #e2e8f0;
  --color-border-light: #f1f5f9;
  
  /* Typography */
  --font-display: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-body: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;

  /* Spacing */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;

  /* Border Radius */
  --radius-sm: 0.375rem;
  --radius-md: 0.75rem;
  --radius-lg: 1rem;
  --radius-xl: 1.5rem;
  --radius-full: 9999px;

  /* Elevation & Shadows */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.07), 0 2px 4px -2px rgba(0, 0, 0, 0.05);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.08), 0 4px 6px -4px rgba(0, 0, 0, 0.04);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 8px 10px -6px rgba(0, 0, 0, 0.04);
  --shadow-accent: 0 10px 20px -5px rgba(37, 99, 235, 0.3);

  /* Transition & Springs */
  --ease-spring: cubic-bezier(0.34, 1.56, 0.64, 1);
  --transition-fast: 0.15s ease;
  --transition-normal: 0.25s ease;
}

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

html {
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.6;
  color: var(--color-text);
  background-color: var(--color-bg);
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  overflow-x: hidden;
  min-height: 100vh;
  position: relative;
  /* Mobile padding to prevent Sticky Bar occlusion */
  padding-bottom: 0;
}

@media (max-width: 768px) {
  body {
    padding-bottom: calc(76px + env(safe-area-inset-bottom));
  }
}

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--color-accent-hover);
}

img, svg {
  display: block;
  max-width: 100%;
  height: auto;
}

/* Typography Helpers */
h1, h2, h3, h4 {
  font-family: var(--font-display);
  color: var(--color-text);
  line-height: 1.25;
  font-weight: 700;
}

.gradient-text {
  background: linear-gradient(135deg, var(--color-accent) 0%, #3b82f6 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  color: var(--color-accent); /* Fallback */
}

.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--space-4);
}

@media (min-width: 640px) { .container { padding: 0 var(--space-6); } }
@media (min-width: 1024px) { .container { padding: 0 var(--space-8); } }

/* Header & Nav */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: var(--color-surface-translucent);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border-light);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 72px;
}

.brand-logo {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: 1.25rem;
  font-weight: 800;
  color: var(--color-text);
  letter-spacing: -0.02em;
}

.brand-icon {
  width: 36px;
  height: 36px;
  background: linear-gradient(135deg, var(--color-accent), #3b82f6);
  color: #ffffff;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 900;
  font-size: 1.2rem;
  box-shadow: var(--shadow-sm);
}

.main-nav {
  display: flex;
  align-items: center;
  gap: var(--space-6);
}

.nav-link {
  color: var(--color-text-muted);
  font-weight: 500;
  font-size: 0.95rem;
}

.nav-link:hover {
  color: var(--color-accent);
}

/* Nav Mobile Toggle */
.mobile-nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--space-2);
  color: var(--color-text);
}

@media (max-width: 768px) {
  .mobile-nav-toggle { display: block; }
  .main-nav {
    display: none;
    position: absolute;
    top: 72px;
    left: 0;
    width: 100%;
    background-color: var(--color-surface);
    flex-direction: column;
    padding: var(--space-6);
    border-bottom: 1px solid var(--color-border);
    box-shadow: var(--shadow-lg);
  }
  .main-nav.is-open { display: flex; }
}

/* Button System */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  font-family: var(--font-body);
  font-weight: 600;
  font-size: 1rem;
  padding: 0.75rem 1.5rem;
  border-radius: var(--radius-md);
  border: 1px solid transparent;
  cursor: pointer;
  transition: transform 0.28s var(--ease-spring), box-shadow var(--transition-fast), background-color var(--transition-fast);
  white-space: nowrap;
}

.btn-primary {
  background-color: var(--color-accent);
  color: #ffffff;
  box-shadow: var(--shadow-accent);
}

.btn-primary:hover {
  background-color: var(--color-accent-hover);
  color: #ffffff;
  transform: translateY(-2px);
  box-shadow: 0 12px 24px -6px rgba(37, 99, 235, 0.4);
}

.btn-primary:active {
  transform: translateY(0);
}

.btn-secondary {
  background: #ffffff !important;
  color: #1e293b !important;
  border: 1.5px solid var(--color-accent) !important;
  box-shadow: 0 2px 8px rgba(0,0,0,0.05);
}

.btn-secondary:hover {
  background-color: var(--color-accent) !important;
  color: #ffffff !important;
  border-color: var(--color-accent) !important;
  transform: translateY(-2px);
}

.btn-lg {
  padding: 1rem 2rem;
  font-size: 1.1rem;
  border-radius: var(--radius-lg);
}

.btn-block {
  width: 100%;
}

/* Hero Section */
.hero-section {
  padding: var(--space-12) 0 var(--space-16);
  position: relative;
  overflow: hidden;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-8);
  align-items: center;
}

@media (min-width: 1024px) {
  .hero-grid {
    grid-template-columns: 1.1fr 0.9fr;
  }
}

.hero-content {
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
}

.hero-title {
  font-size: 2.25rem;
  letter-spacing: -0.03em;
  line-height: 1.15;
}

@media (min-width: 640px) { .hero-title { font-size: 3rem; } }
@media (min-width: 1024px) { .hero-title { font-size: 3.5rem; } }

.hero-subtitle {
  font-size: 1.125rem;
  color: var(--color-text-muted);
  max-width: 600px;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-4);
}

/* Trust Pills (Hero) */
.trust-pills {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
  margin-top: var(--space-2);
}

.trust-pill {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  background-color: var(--color-accent-light);
  color: var(--color-accent-hover);
  padding: 0.4rem 0.85rem;
  border-radius: var(--radius-full);
  font-size: 0.875rem;
  font-weight: 600;
  border: 1px solid var(--color-accent-border);
}

.trust-microcopy {
  font-size: 0.875rem;
  color: var(--color-text-light);
  margin-top: var(--space-1);
}

/* Hero Visual SVG Card */
.hero-visual {
  position: relative;
  display: flex;
  justify-content: center;
}

.hero-card-preview {
  width: 100%;
  max-width: 480px;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  padding: var(--space-6);
  box-shadow: var(--shadow-xl);
  position: relative;
}

.pulse-node {
  animation: pulseSvg 2.5s infinite ease-in-out;
}

@keyframes pulseSvg {
  0%, 100% { opacity: 0.4; transform: scale(1); }
  50% { opacity: 1; transform: scale(1.05); }
}

/* Section Styling */
.section {
  padding: var(--space-16) 0;
}

.section-alt {
  background-color: var(--color-surface);
  border-top: 1px solid var(--color-border-light);
  border-bottom: 1px solid var(--color-border-light);
}

.section-header {
  text-align: center;
  max-width: 700px;
  margin: 0 auto var(--space-12);
}

.section-title {
  font-size: 2rem;
  margin-bottom: var(--space-3);
}

@media (min-width: 768px) { .section-title { font-size: 2.5rem; } }

.section-desc {
  font-size: 1.1rem;
  color: var(--color-text-muted);
}

/* Features Grid */
.features-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-6);
}

@media (min-width: 768px) {
  .features-grid { grid-template-columns: repeat(3, 1fr); }
}

.feature-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-8);
  transition: transform var(--transition-normal), box-shadow var(--transition-normal);
}

.feature-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: var(--color-accent-border);
}

.feature-icon {
  width: 48px;
  height: 48px;
  background-color: var(--color-accent-light);
  color: var(--color-accent);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  margin-bottom: var(--space-4);
}

.feature-card h3 {
  font-size: 1.25rem;
  margin-bottom: var(--space-2);
}

.feature-card p {
  color: var(--color-text-muted);
  font-size: 0.95rem;
}

/* Unlocks Showcase Grid */
.unlocks-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-4);
}

@media (min-width: 640px) { .unlocks-grid { grid-template-columns: repeat(4, 1fr); } }

.unlock-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: var(--space-4);
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-2);
  font-weight: 600;
  font-size: 0.95rem;
}

.unlock-tag {
  font-size: 0.75rem;
  color: var(--color-success);
  background: var(--color-success-bg);
  padding: 0.1rem 0.5rem;
  border-radius: var(--radius-full);
}

/* Pricing Section */
.promo-banner {
  background: linear-gradient(135deg, #eff6ff 0%, #dbeafe 100%);
  border: 1px solid var(--color-accent-border);
  border-radius: var(--radius-md);
  padding: var(--space-4) var(--space-6);
  text-align: center;
  font-weight: 600;
  color: var(--color-accent-hover);
  margin-bottom: var(--space-8);
  font-size: 1.05rem;
}

.promo-code-pill {
  background: #ffffff;
  padding: 0.2rem 0.6rem;
  border-radius: var(--radius-sm);
  border: 1px dashed var(--color-accent);
  color: var(--color-accent-hover);
  font-family: monospace;
  font-weight: 700;
}

.pricing-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-6);
  align-items: stretch;
}

@media (min-width: 768px) {
  .pricing-grid { grid-template-columns: repeat(3, 1fr); }
}

.pricing-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  padding: var(--space-8);
  display: flex;
  flex-direction: column;
  position: relative;
  transition: transform var(--transition-normal), box-shadow var(--transition-normal);
}

.pricing-card.featured {
  border: 2px solid var(--color-accent);
  box-shadow: var(--shadow-xl);
  transform: scale(1.03);
}

@media (max-width: 767px) {
  .pricing-card.featured { transform: scale(1); }
}

.badge-featured {
  position: absolute;
  top: -14px;
  left: 50%;
  transform: translateX(-50%);
  background: var(--color-accent);
  color: #ffffff;
  font-size: 0.8rem;
  font-weight: 700;
  padding: 0.25rem 0.85rem;
  border-radius: var(--radius-full);
}

.pricing-header {
  margin-bottom: var(--space-6);
}

.plan-name {
  font-size: 1.25rem;
  margin-bottom: var(--space-2);
}

.plan-price {
  font-size: 2.5rem;
  font-weight: 800;
  color: var(--color-text);
  line-height: 1;
}

.plan-price span {
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--color-text-muted);
}

.pricing-features {
  list-style: none;
  margin-bottom: var(--space-8);
  flex-grow: 1;
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.pricing-features li {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: 0.95rem;
  color: var(--color-text-muted);
}

.pricing-features li::before {
  content: "✓";
  color: var(--color-success);
  font-weight: 800;
}

.pricing-footer {
  text-align: center;
}

.refund-guarantee {
  display: block;
  margin-top: var(--space-3);
  font-size: 0.85rem;
  color: var(--color-text-light);
  font-weight: 500;
}

/* Comparison Table */
.table-responsive {
  width: 100%;
  overflow-x: auto;
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-border);
  background: var(--color-surface);
}

.comparison-table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
  font-size: 0.95rem;
}

.comparison-table th, .comparison-table td {
  padding: var(--space-4) var(--space-6);
  border-bottom: 1px solid var(--color-border-light);
}

.comparison-table th {
  background: var(--color-surface-hover);
  font-weight: 700;
}

/* FAQ Accordion */
.faq-list {
  max-width: 800px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}

.faq-item {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  overflow: hidden;
}

.faq-question {
  width: 100%;
  padding: var(--space-4) var(--space-6);
  background: none;
  border: none;
  text-align: left;
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--color-text);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.faq-answer {
  padding: 0 var(--space-6) var(--space-6);
  color: var(--color-text-muted);
  display: none;
  font-size: 0.95rem;
}

.faq-item.is-open .faq-answer {
  display: block;
}

.faq-item.is-open .faq-icon {
  transform: rotate(180deg);
}

.faq-icon {
  transition: transform var(--transition-fast);
}

/* Footer */
.site-footer {
  background: #0f172a;
  color: #94a3b8;
  padding: var(--space-12) 0 var(--space-8);
  border-top: 1px solid var(--color-border);
}

.footer-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-8);
  margin-bottom: var(--space-8);
}

@media (min-width: 768px) {
  .footer-grid { grid-template-columns: 2fr 1fr 1fr 1fr; }
}

.footer-col h4 {
  color: #ffffff;
  font-size: 1rem;
  margin-bottom: var(--space-4);
}

.footer-links {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.footer-links a {
  color: #94a3b8;
  font-size: 0.9rem;
}

.footer-links a:hover {
  color: #ffffff;
}

.footer-bottom {
  border-top: 1px solid #1e293b;
  padding-top: var(--space-6);
  text-align: center;
  font-size: 0.85rem;
}

/* Sticky Mobile CTA Bar (C4 Component) */
.mobile-sticky-bar {
  display: none;
  position: fixed;
  bottom: 0;
  left: 0;
  width: 100%;
  background: var(--color-surface-translucent);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-top: 1px solid var(--color-border);
  padding: var(--space-3) var(--space-4);
  padding-bottom: calc(var(--space-3) + env(safe-area-inset-bottom));
  z-index: 90;
  box-shadow: 0 -4px 12px rgba(0, 0, 0, 0.08);
}

@media (max-width: 768px) {
  .mobile-sticky-bar {
    display: flex;
    gap: var(--space-3);
  }
}

.mobile-sticky-bar .btn {
  flex: 1;
  padding: 0.65rem 0.5rem;
  font-size: 0.9rem;
}

/* Exit-Intent Modal (C5 Component) */
.modal-overlay {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  background: rgba(15, 23, 42, 0.6);
  backdrop-filter: blur(4px);
  z-index: 200;
  align-items: center;
  justify-content: center;
  padding: var(--space-4);
}

.modal-overlay.is-active {
  display: flex;
}

.modal-container {
  background: var(--color-surface);
  border-radius: var(--radius-xl);
  max-width: 460px;
  width: 100%;
  padding: var(--space-8);
  position: relative;
  box-shadow: var(--shadow-xl);
  border: 1px solid var(--color-border);
  animation: modalFadeIn 0.25s ease-out;
}

@keyframes modalFadeIn {
  from { opacity: 0; transform: scale(0.95); }
  to { opacity: 1; transform: scale(1); }
}

.modal-close {
  position: absolute;
  top: var(--space-4);
  right: var(--space-4);
  background: none;
  border: none;
  font-size: 1.5rem;
  color: var(--color-text-light);
  cursor: pointer;
  line-height: 1;
}

.modal-title {
  font-size: 1.5rem;
  margin-bottom: var(--space-2);
}

.modal-desc {
  color: var(--color-text-muted);
  font-size: 0.95rem;
  margin-bottom: var(--space-6);
}

.promo-box {
  background: var(--color-accent-light);
  border: 1px dashed var(--color-accent);
  border-radius: var(--radius-md);
  padding: var(--space-4);
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--space-6);
}

.promo-code-text {
  font-family: monospace;
  font-size: 1.25rem;
  font-weight: 800;
  color: var(--color-accent-hover);
}

.copy-btn {
  background: var(--color-accent);
  color: #ffffff;
  border: none;
  padding: 0.4rem 0.85rem;
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
  transition: background-color var(--transition-fast);
}

.copy-btn.copied {
  background: var(--color-success);
}

.modal-trust {
  margin-top: var(--space-3);
  text-align: center;
  font-size: 0.85rem;
  color: var(--color-text-light);
}

/* Reduced Motion */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

/* Mobile Responsive Overhaul (Zero Horizontal Scroll & Card Layout) */
@media (max-width: 768px) {
  html, body {
    overflow-x: hidden !important;
    width: 100% !important;
    max-width: 100vw !important;
    padding-bottom: 90px !important;
  }

  .container {
    padding-left: var(--space-4) !important;
    padding-right: var(--space-4) !important;
    width: 100% !important;
    max-width: 100% !important;
    box-sizing: border-box !important;
  }

  .table-responsive {
    overflow-x: visible !important;
    border: none !important;
    background: transparent !important;
    box-shadow: none !important;
  }

  .comparison-table,
  .comparison-table tbody,
  .comparison-table tr,
  .comparison-table td {
    display: block !important;
    width: 100% !important;
    box-sizing: border-box !important;
  }

  .comparison-table thead {
    display: none !important;
  }

  .comparison-table tr {
    background: var(--color-surface) !important;
    border: 1px solid var(--color-border) !important;
    border-radius: var(--radius-lg) !important;
    padding: var(--space-4) !important;
    margin-bottom: var(--space-4) !important;
    box-shadow: var(--shadow-sm) !important;
  }

  .comparison-table td {
    padding: var(--space-3) 0 !important;
    border-bottom: 1px dashed var(--color-border-light) !important;
    display: flex !important;
    justify-content: space-between !important;
    align-items: center !important;
    font-size: 0.9rem !important;
    text-align: right !important;
  }

  .comparison-table td:last-child {
    border-bottom: none !important;
  }

  .comparison-table td:first-child {
    font-size: 1.05rem !important;
    font-weight: 700 !important;
    color: var(--color-accent) !important;
    border-bottom: 2px solid var(--color-border) !important;
    padding-bottom: var(--space-3) !important;
    margin-bottom: var(--space-2) !important;
    display: block !important;
    text-align: left !important;
  }

  .comparison-table td:nth-child(2)::before { content: "传输协议"; font-weight: 600; color: var(--color-text-muted); }
  .comparison-table td:nth-child(3)::before { content: "晚高峰延迟"; font-weight: 600; color: var(--color-text-muted); }
  .comparison-table td:nth-child(4)::before { content: "4K 加载时间"; font-weight: 600; color: var(--color-text-muted); }
  .comparison-table td:nth-child(5)::before { content: "ChatGPT 解锁"; font-weight: 600; color: var(--color-text-muted); }
}