/* 
   星云VPN - Minimal Daytime Observatory Stylesheet
   Color Palette:
   - Primary White: #FFFFFF
   - Cosmic Navy: #27334F
   - Muted Periwinkle: #8C9FCE
   - Pale Cloud: #F0F2F8
*/

:root {
  --color-white: #FFFFFF;
  --color-navy: #27334F;
  --color-periwinkle: #8C9FCE;
  --color-cloud: #F0F2F8;
  --color-cloud-hover: #E2E8F4;
  --color-border: #E2E8F0;
  --color-text-muted: #5A6B8B;
  --font-sans: system-ui, -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Segoe UI", Roboto, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  --container-max: 1200px;
}

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

html {
  scroll-behavior: smooth;
  font-size: 16px;
  background-color: var(--color-white);
  color: var(--color-navy);
  font-family: var(--font-sans);
  -webkit-font-smoothing: antialiased;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  line-height: 1.7;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  color: var(--color-navy);
  font-weight: 300;
  line-height: 1.25;
}

h1 {
  font-size: 38px;
  letter-spacing: -0.02em;
  font-weight: 300;
}

@media (min-width: 1024px) {
  h1 {
    font-size: 62px;
  }
}

h2 {
  font-size: 28px;
  font-weight: 300;
  margin-bottom: 1rem;
}

@media (min-width: 768px) {
  h2 {
    font-size: 36px;
  }
}

h3 {
  font-size: 20px;
  font-weight: 400;
  margin-bottom: 0.75rem;
}

p {
  margin-bottom: 1rem;
  color: var(--color-navy);
}

.text-muted {
  color: var(--color-text-muted);
}

.coord-label {
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--color-periwinkle);
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

/* Layout Utilities */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 1.5rem;
}

.section {
  padding: 4rem 0;
  position: relative;
}

@media (min-width: 768px) {
  .section {
    padding: 6rem 0;
  }
}

.bg-cloud {
  background-color: var(--color-cloud);
}

.bg-white {
  background-color: var(--color-white);
}

.section-header {
  text-align: center;
  max-width: 720px;
  margin: 0 auto 3rem auto;
}

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

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.85rem 1.75rem;
  font-size: 1rem;
  font-weight: 500;
  border-radius: 6px;
  text-decoration: none;
  transition: all 0.25s ease;
  cursor: pointer;
  border: 1px solid transparent;
}

.btn-primary {
  background-color: var(--color-navy);
  color: var(--color-white);
  border-color: var(--color-navy);
}

.btn-primary:hover, .btn-primary:focus {
  background-color: #1A2438;
  border-color: #1A2438;
  color: var(--color-white);
  box-shadow: 0 4px 12px rgba(39, 51, 79, 0.15);
}

.btn-secondary {
  background-color: var(--color-white);
  color: var(--color-navy);
  border-color: var(--color-periwinkle);
}

.btn-secondary:hover, .btn-secondary:focus {
  background-color: var(--color-cloud);
  border-color: var(--color-navy);
}

/* Header Navigation */
.header {
  position: sticky;
  top: 0;
  z-index: 1000;
  background-color: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--color-border);
  transition: background-color 0.3s;
}

.header-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 4.5rem;
}

.logo {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  text-decoration: none;
  color: var(--color-navy);
  font-weight: 600;
  font-size: 1.25rem;
}

.logo-icon {
  width: 36px;
  height: 36px;
}

.nav-links {
  display: none;
  list-style: none;
  gap: 2rem;
  align-items: center;
}

@media (min-width: 992px) {
  .nav-links {
    display: flex;
  }
}

.nav-link {
  text-decoration: none;
  color: var(--color-navy);
  font-size: 0.95rem;
  transition: color 0.2s;
}

.nav-link:hover, .nav-link:focus {
  color: var(--color-periwinkle);
}

.nav-cta {
  display: none;
}

@media (min-width: 992px) {
  .nav-cta {
    display: inline-flex;
  }
}

/* Mobile Toggle */
.menu-toggle {
  display: flex;
  flex-direction: column;
  justify-content: space-around;
  width: 30px;
  height: 24px;
  background: transparent;
  border: none;
  cursor: pointer;
  padding: 0;
  z-index: 1001;
}

@media (min-width: 992px) {
  .menu-toggle {
    display: none;
  }
}

.menu-toggle span {
  width: 100%;
  height: 2px;
  background-color: var(--color-navy);
  transition: all 0.3s ease;
  transform-origin: 1px;
}

.mobile-menu {
  position: fixed;
  top: 4.5rem;
  left: 0;
  width: 100%;
  background-color: var(--color-white);
  border-bottom: 1px solid var(--color-border);
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
  transform: translateY(-150%);
  transition: transform 0.3s ease-in-out;
  box-shadow: 0 10px 20px rgba(0, 0, 0, 0.05);
  z-index: 999;
}

.mobile-menu.active {
  transform: translateY(0);
}

.mobile-menu a {
  text-decoration: none;
  color: var(--color-navy);
  font-size: 1.1rem;
  padding: 0.5rem 0;
  border-bottom: 1px solid var(--color-cloud);
}

/* Hero Section */
.hero {
  padding: 4rem 0 5rem 0;
  overflow: hidden;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 3rem;
  align-items: center;
}

@media (min-width: 992px) {
  .hero-grid {
    grid-template-columns: 1fr 1fr;
  }
}

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

.hero-tag {
  display: inline-block;
  padding: 0.35rem 0.85rem;
  background-color: var(--color-cloud);
  border: 1px solid var(--color-periwinkle);
  border-radius: 20px;
  font-size: 0.85rem;
  margin-bottom: 1.5rem;
}

.hero-desc {
  font-size: 1.15rem;
  color: var(--color-text-muted);
  margin: 1.5rem 0 2rem 0;
  max-width: 540px;
}

.hero-actions {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
}

/* Orbital Dashboard SVG & CSS */
.dashboard-card {
  background-color: var(--color-cloud);
  border: 1px solid var(--color-border);
  border-radius: 16px;
  padding: 1.5rem;
  position: relative;
  box-shadow: 0 10px 30px rgba(39, 51, 79, 0.04);
}

.dashboard-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1rem;
  padding-bottom: 0.75rem;
  border-bottom: 1px solid rgba(140, 159, 206, 0.3);
}

.dashboard-svg {
  width: 100%;
  height: auto;
  display: block;
}

/* Animation for slow orbit line - SVG stroke-dashoffset or rotation line */
.orbit-line {
  transform-origin: 200px 200px;
  animation: orbitRotate 30s linear infinite;
}

.orbit-pulse {
  animation: orbitPulse 4s ease-in-out infinite alternate;
}

@keyframes orbitRotate {
  from {
    transform: rotate(0deg);
  }
  to {
    transform: rotate(360deg);
  }
}

@keyframes orbitPulse {
  0% {
    stroke-opacity: 0.3;
  }
  100% {
    stroke-opacity: 0.8;
  }
}

@media (prefers-reduced-motion: reduce) {
  .orbit-line, .orbit-pulse {
    animation: none !important;
  }
}

/* Three Advantages Section: Radial + 2 Columns */
.advantages-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2rem;
  align-items: center;
}

@media (min-width: 992px) {
  .advantages-grid {
    grid-template-columns: 1.2fr 1fr 1fr;
  }
}

.radial-container {
  background-color: var(--color-white);
  border: 1px solid var(--color-border);
  border-radius: 16px;
  padding: 2rem;
  text-align: center;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.02);
}

.advantage-card {
  background-color: var(--color-white);
  border: 1px solid var(--color-border);
  border-radius: 16px;
  padding: 2rem;
  height: 100%;
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.advantage-icon {
  width: 48px;
  height: 48px;
  background-color: var(--color-cloud);
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 1.25rem;
  color: var(--color-navy);
}

/* Global Nodes Section */
.nodes-legend {
  display: flex;
  justify-content: center;
  gap: 2rem;
  flex-wrap: wrap;
  margin-bottom: 2.5rem;
  padding: 1rem;
  background-color: var(--color-white);
  border-radius: 8px;
  border: 1px solid var(--color-border);
}

.legend-item {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.9rem;
}

.legend-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
}

.legend-dot.transit { background-color: var(--color-navy); }
.legend-dot.bgp { background-color: var(--color-periwinkle); }
.legend-dot.dispatch { border: 2px solid var(--color-navy); background: transparent; }

.nodes-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.5rem;
}

@media (min-width: 640px) {
  .nodes-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1024px) {
  .nodes-grid {
    grid-template-columns: repeat(4, 1fr);
  }
}

.node-card {
  background-color: var(--color-white);
  border: 1px solid var(--color-border);
  border-radius: 12px;
  padding: 1.5rem;
  transition: transform 0.2s, box-shadow 0.2s;
}

.node-card:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(39, 51, 79, 0.06);
}

.node-flag {
  font-size: 1.5rem;
  margin-bottom: 0.5rem;
}

/* AI / Streaming Use Cases */
.usecases-container {
  display: flex;
  flex-direction: column;
  gap: 3rem;
}

.usecase-block {
  background-color: var(--color-white);
  border: 1px solid var(--color-border);
  border-radius: 16px;
  padding: 2.5rem;
  display: grid;
  grid-template-columns: 1fr;
  gap: 2rem;
  align-items: center;
}

@media (min-width: 992px) {
  .usecase-block {
    grid-template-columns: 1fr 1fr;
  }
  .usecase-block.reverse {
    grid-template-columns: 1fr 1fr;
  }
  .usecase-block.reverse .usecase-info {
    order: 2;
  }
  .usecase-block.reverse .usecase-diagram {
    order: 1;
  }
}

.usecase-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 1rem;
}

.tag-badge {
  padding: 0.3rem 0.75rem;
  background-color: var(--color-cloud);
  border-radius: 4px;
  font-size: 0.85rem;
  color: var(--color-navy);
  border: 1px solid var(--color-border);
}

/* Pricing Grid */
.pricing-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2rem;
}

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

.pricing-card {
  background-color: var(--color-white);
  border: 1px solid var(--color-border);
  border-radius: 16px;
  padding: 2.5rem 2rem;
  display: flex;
  flex-direction: column;
  position: relative;
  transition: border-color 0.3s, box-shadow 0.3s;
}

.pricing-card.featured {
  border-color: var(--color-navy);
  box-shadow: 0 10px 30px rgba(39, 51, 79, 0.08);
}

.pricing-card.featured::before {
  content: "最受欢迎";
  position: absolute;
  top: -12px;
  right: 20px;
  background-color: var(--color-navy);
  color: var(--color-white);
  font-size: 0.75rem;
  padding: 0.2rem 0.75rem;
  border-radius: 10px;
}

.pricing-price {
  font-size: 1.5rem;
  font-weight: 400;
  margin: 1rem 0;
  color: var(--color-navy);
}

.pricing-placeholder {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  background-color: var(--color-cloud);
  padding: 0.5rem 0.75rem;
  border-radius: 6px;
  margin-bottom: 1.5rem;
}

.pricing-features {
  list-style: none;
  margin-bottom: 2rem;
  flex-grow: 1;
}

.pricing-features li {
  padding: 0.5rem 0;
  border-bottom: 1px dashed var(--color-border);
  font-size: 0.95rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

/* Article Cards Section (3 desktop / 2 tablet / 1 mobile) */
.articles-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.5rem;
}

@media (min-width: 640px) {
  .articles-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1024px) {
  .articles-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}

.article-card {
  background-color: var(--color-white);
  border: 1px solid var(--color-border);
  border-radius: 12px;
  padding: 1.75rem;
  display: flex;
  flex-direction: column;
  position: relative;
  transition: transform 0.2s, border-color 0.2s;
  overflow: hidden;
}

.article-card::after {
  content: "";
  position: absolute;
  top: 12px;
  right: 12px;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background-color: var(--color-periwinkle);
  box-shadow: -10px 10px 0 -1px var(--color-periwinkle), 0 15px 0 -2px var(--color-navy);
  opacity: 0.6;
}

.article-card:hover {
  transform: translateY(-3px);
  border-color: var(--color-periwinkle);
}

.article-meta {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1rem;
}

.article-title {
  font-size: 1.2rem;
  font-weight: 400;
  margin-bottom: 0.75rem;
  line-height: 1.4;
}

.article-title a {
  color: var(--color-navy);
  text-decoration: none;
}

.article-title a:hover {
  color: var(--color-periwinkle);
}

.article-desc {
  font-size: 0.92rem;
  color: var(--color-text-muted);
  margin-bottom: 1.5rem;
  flex-grow: 1;
}

.article-link {
  color: var(--color-navy);
  font-weight: 500;
  font-size: 0.9rem;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
}

.article-link:hover {
  text-decoration: underline;
}

/* Testimonials */
.testimonials-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.5rem;
}

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

.testimonial-card {
  background-color: var(--color-white);
  border: 1px solid var(--color-border);
  border-radius: 12px;
  padding: 1.75rem;
}

.testimonial-quote {
  font-size: 0.95rem;
  color: var(--color-navy);
  margin-bottom: 1.25rem;
  font-style: normal;
}

.testimonial-author {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.avatar-placeholder {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background-color: var(--color-cloud);
  border: 1px solid var(--color-periwinkle);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--color-navy);
}

/* FAQ Accordion */
.faq-list {
  max-width: 800px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.faq-item {
  background-color: var(--color-white);
  border: 1px solid var(--color-border);
  border-radius: 10px;
  overflow: hidden;
}

.faq-button {
  width: 100%;
  padding: 1.25rem;
  text-align: left;
  background: none;
  border: none;
  font-size: 1.1rem;
  font-weight: 400;
  color: var(--color-navy);
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.faq-icon {
  transition: transform 0.3s;
}

.faq-button[aria-expanded="true"] .faq-icon {
  transform: rotate(180deg);
}

.faq-content {
  padding: 0 1.25rem 1.25rem 1.25rem;
  font-size: 0.98rem;
  color: var(--color-text-muted);
}

.faq-content[hidden] {
  display: none;
}

/* Footer */
.footer {
  background-color: var(--color-cloud);
  border-top: 1px solid var(--color-border);
  padding: 4rem 0 2rem 0;
  margin-top: auto;
}

.footer-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2.5rem;
  margin-bottom: 3rem;
}

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

.footer-col h4 {
  font-size: 1rem;
  font-weight: 500;
  margin-bottom: 1.2rem;
  color: var(--color-navy);
}

.footer-links {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}

.footer-links a {
  color: var(--color-text-muted);
  text-decoration: none;
  font-size: 0.9rem;
  transition: color 0.2s;
}

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

.footer-bottom {
  padding-top: 2rem;
  border-top: 1px solid var(--color-border);
  text-align: center;
  font-size: 0.85rem;
  color: var(--color-text-muted);
}

/* Article Detail Styles */
.article-header {
  padding: 3rem 0 2rem 0;
  background-color: var(--color-cloud);
  border-bottom: 1px solid var(--color-border);
}

.breadcrumb {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  list-style: none;
  font-size: 0.88rem;
  margin-bottom: 1.5rem;
  flex-wrap: wrap;
}

.breadcrumb a {
  color: var(--color-text-muted);
  text-decoration: none;
}

.breadcrumb a:hover {
  color: var(--color-navy);
}

.breadcrumb-separator {
  color: var(--color-periwinkle);
}

.article-content {
  max-width: 860px;
  margin: 0 auto;
  padding: 3rem 1.5rem;
}

.article-body {
  font-size: 1.05rem;
  line-height: 1.85;
}

.article-body h2 {
  margin-top: 2.5rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--color-border);
}

.article-body h3 {
  margin-top: 1.8rem;
}

.article-body ul, .article-body ol {
  margin: 1rem 0 1.5rem 1.5rem;
}

.article-body li {
  margin-bottom: 0.5rem;
}

.related-articles {
  margin-top: 4rem;
  padding-top: 2.5rem;
  border-top: 1px solid var(--color-border);
}

.callout-box {
  background-color: var(--color-cloud);
  border-left: 4px solid var(--color-periwinkle);
  padding: 1.25rem 1.5rem;
  border-radius: 0 8px 8px 0;
  margin: 1.5rem 0;
}

/* Accessibility focus indicator */
a:focus-visible, button:focus-visible {
  outline: 2px solid var(--color-navy);
  outline-offset: 2px;
}