/* ===== CSS Variables ===== */
:root {
  --color-primary: #e8760a;
  --color-primary-dark: #c46208;
  --color-primary-light: #f59e42;
  --color-bg-dark: #0f172a;
  --color-bg-darker: #020617;
  --color-bg-card: #1e293b;
  --color-bg-card-hover: #273548;
  --color-text: #e2e8f0;
  --color-text-muted: #94a3b8;
  --color-text-dim: #64748b;
  --color-border: #334155;
  --color-accent: #38bdf8;
  --font-sans: "PingFang SC", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  --font-mono: "Cascadia Code", "Fira Code", Consolas, monospace;
  --radius: 12px;
  --radius-sm: 8px;
  --shadow: 0 4px 24px rgba(0, 0, 0, 0.3);
  --shadow-lg: 0 8px 40px rgba(0, 0, 0, 0.4);
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --header-height: 72px;
}

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

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: var(--font-sans);
  background: var(--color-bg-darker);
  color: var(--color-text);
  line-height: 1.7;
  overflow-x: hidden;
}

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

a:hover {
  color: var(--color-primary-light);
}

img {
  max-width: 100%;
  display: block;
}

ul {
  list-style: none;
}

.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
}

.container-narrow {
  max-width: 800px;
}

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

.section {
  padding: 100px 0;
}

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

.section-header {
  text-align: center;
  margin-bottom: 64px;
}

.section-tag {
  display: inline-block;
  padding: 6px 16px;
  background: rgba(232, 118, 10, 0.15);
  color: var(--color-primary-light);
  border-radius: 20px;
  font-size: 0.875rem;
  font-weight: 500;
  letter-spacing: 0.05em;
  margin-bottom: 16px;
}

.section-title {
  font-size: 2.5rem;
  font-weight: 700;
  color: #fff;
  margin-bottom: 16px;
  line-height: 1.3;
}

.section-desc {
  font-size: 1.125rem;
  color: var(--color-text-muted);
  max-width: 600px;
  margin: 0 auto;
}

/* ===== Header & Nav ===== */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  height: var(--header-height);
  background: rgba(2, 6, 23, 0.85);
  backdrop-filter: blur(16px);
  border-bottom: 1px solid transparent;
  transition: border-color var(--transition), background var(--transition);
}

.header.scrolled {
  border-bottom-color: var(--color-border);
  background: rgba(2, 6, 23, 0.95);
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  color: #fff;
  font-size: 1.25rem;
  font-weight: 700;
  text-decoration: none;
}

.logo:hover {
  color: #fff;
}

.logo-icon {
  font-size: 1.5rem;
}

.nav-menu {
  display: flex;
  gap: 8px;
}

.nav-menu a {
  display: block;
  padding: 8px 20px;
  color: var(--color-text-muted);
  font-size: 0.9375rem;
  font-weight: 500;
  border-radius: var(--radius-sm);
  transition: all var(--transition);
}

.nav-menu a:hover,
.nav-menu a.active {
  color: #fff;
  background: rgba(255, 255, 255, 0.08);
}

.nav-menu a.active {
  color: var(--color-primary-light);
}

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 8px;
}

.nav-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: #fff;
  border-radius: 2px;
  transition: all var(--transition);
}

.nav-toggle.active span:nth-child(1) {
  transform: rotate(45deg) translate(5px, 5px);
}

.nav-toggle.active span:nth-child(2) {
  opacity: 0;
}

.nav-toggle.active span:nth-child(3) {
  transform: rotate(-45deg) translate(5px, -5px);
}

/* ===== Buttons ===== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 14px 32px;
  font-size: 1rem;
  font-weight: 600;
  border-radius: var(--radius-sm);
  border: 2px solid transparent;
  cursor: pointer;
  transition: all var(--transition);
  text-decoration: none;
}

.btn-primary {
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-dark));
  color: #fff;
  box-shadow: 0 4px 16px rgba(232, 118, 10, 0.35);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 24px rgba(232, 118, 10, 0.45);
  color: #fff;
}

.btn-outline {
  background: transparent;
  color: #fff;
  border-color: rgba(255, 255, 255, 0.3);
}

.btn-outline:hover {
  border-color: var(--color-primary);
  color: var(--color-primary-light);
  background: rgba(232, 118, 10, 0.1);
}

/* ===== Hero ===== */
.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding-top: var(--header-height);
  overflow: hidden;
}

.hero-bg {
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse 80% 60% at 50% 0%, rgba(232, 118, 10, 0.15), transparent),
    radial-gradient(ellipse 60% 50% at 80% 50%, rgba(56, 189, 248, 0.08), transparent),
    linear-gradient(180deg, var(--color-bg-dark) 0%, var(--color-bg-darker) 100%);
}

.hero-bg::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(255, 255, 255, 0.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255, 255, 255, 0.03) 1px, transparent 1px);
  background-size: 60px 60px;
  mask-image: radial-gradient(ellipse 70% 60% at 50% 40%, black, transparent);
}

.hero-content {
  position: relative;
  text-align: center;
  padding: 60px 24px;
}

.hero-badge {
  display: inline-block;
  padding: 8px 20px;
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 24px;
  font-size: 0.875rem;
  color: var(--color-text-muted);
  margin-bottom: 32px;
  animation: fadeInUp 0.8s ease;
}

.hero-title {
  font-size: clamp(2.5rem, 6vw, 4rem);
  font-weight: 800;
  color: #fff;
  line-height: 1.2;
  margin-bottom: 24px;
  animation: fadeInUp 0.8s ease 0.1s both;
}

.hero-title .highlight {
  background: linear-gradient(135deg, var(--color-primary-light), var(--color-primary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-desc {
  font-size: 1.2rem;
  color: var(--color-text-muted);
  max-width: 640px;
  margin: 0 auto 40px;
  animation: fadeInUp 0.8s ease 0.2s both;
}

.hero-actions {
  display: flex;
  gap: 16px;
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: 64px;
  animation: fadeInUp 0.8s ease 0.3s both;
}

.hero-stats {
  display: flex;
  gap: 48px;
  justify-content: center;
  animation: fadeInUp 0.8s ease 0.4s both;
}

.stat-item {
  display: flex;
  flex-direction: column;
  align-items: center;
}

.stat-num {
  font-size: 2.5rem;
  font-weight: 800;
  color: var(--color-primary-light);
  line-height: 1;
}

.stat-label {
  font-size: 0.875rem;
  color: var(--color-text-dim);
  margin-top: 8px;
}

.hero-scroll {
  position: absolute;
  bottom: 40px;
  left: 50%;
  transform: translateX(-50%);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  color: var(--color-text-dim);
  font-size: 0.8125rem;
  animation: fadeInUp 0.8s ease 0.6s both;
}

.scroll-arrow {
  width: 20px;
  height: 20px;
  border-right: 2px solid var(--color-text-dim);
  border-bottom: 2px solid var(--color-text-dim);
  transform: rotate(45deg);
  animation: bounce 2s infinite;
}

/* ===== Features ===== */
.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 24px;
}

.feature-card {
  padding: 36px 28px;
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  transition: all var(--transition);
}

.feature-card:hover {
  transform: translateY(-4px);
  border-color: rgba(232, 118, 10, 0.3);
  box-shadow: var(--shadow);
  background: var(--color-bg-card-hover);
}

.feature-icon {
  font-size: 2.5rem;
  margin-bottom: 20px;
}

.feature-card h3 {
  font-size: 1.25rem;
  color: #fff;
  margin-bottom: 12px;
}

.feature-card p {
  color: var(--color-text-muted);
  font-size: 0.9375rem;
}

/* ===== Roadmap Timeline (Preview) ===== */
.roadmap-timeline {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 24px;
  position: relative;
}

.timeline-item {
  display: flex;
  gap: 20px;
  padding: 28px;
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  transition: all var(--transition);
}

.timeline-item:hover {
  border-color: var(--color-primary);
  background: rgba(232, 118, 10, 0.06);
  transform: translateY(-2px);
}

.timeline-marker {
  flex-shrink: 0;
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-dark));
  color: #fff;
  font-weight: 800;
  font-size: 0.875rem;
  border-radius: 12px;
  font-family: var(--font-mono);
}

.timeline-content h3 {
  font-size: 1.125rem;
  color: #fff;
  margin-bottom: 6px;
}

.timeline-content p {
  font-size: 0.875rem;
  color: var(--color-text-muted);
}

/* ===== Tech Stack ===== */
.tech-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  justify-content: center;
}

.tech-tag {
  padding: 10px 24px;
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: 24px;
  font-size: 0.9375rem;
  color: var(--color-text-muted);
  transition: all var(--transition);
  cursor: default;
}

.tech-tag:hover {
  border-color: var(--color-primary);
  color: var(--color-primary-light);
  background: rgba(232, 118, 10, 0.08);
}

/* ===== Page Hero (Sub pages) ===== */
.page-hero {
  padding: calc(var(--header-height) + 60px) 0 60px;
  background: var(--color-bg-dark);
  text-align: center;
  border-bottom: 1px solid var(--color-border);
}

.page-hero h1 {
  font-size: 2.75rem;
  font-weight: 800;
  color: #fff;
  margin-bottom: 16px;
}

.page-hero p {
  font-size: 1.125rem;
  color: var(--color-text-muted);
}

/* ===== Roadmap Stages (Detail page) ===== */
.roadmap-stage {
  margin-bottom: 48px;
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  overflow: hidden;
  transition: border-color var(--transition);
}

.roadmap-stage:hover {
  border-color: rgba(232, 118, 10, 0.3);
}

.stage-header {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 28px 32px;
  background: rgba(255, 255, 255, 0.03);
  border-bottom: 1px solid var(--color-border);
  flex-wrap: wrap;
}

.stage-num {
  padding: 6px 14px;
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-dark));
  color: #fff;
  font-size: 0.8125rem;
  font-weight: 700;
  border-radius: 6px;
  font-family: var(--font-mono);
}

.stage-header h2 {
  flex: 1;
  font-size: 1.5rem;
  color: #fff;
}

.stage-duration {
  font-size: 0.875rem;
  color: var(--color-text-dim);
  padding: 4px 12px;
  background: rgba(255, 255, 255, 0.05);
  border-radius: 16px;
}

.stage-body {
  padding: 32px;
}

.stage-intro {
  color: var(--color-text-muted);
  margin-bottom: 28px;
  font-size: 1rem;
  padding-left: 16px;
  border-left: 3px solid var(--color-primary);
}

.topic-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 20px;
}

.topic-card {
  padding: 24px;
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  transition: all var(--transition);
}

.topic-card:hover {
  background: rgba(232, 118, 10, 0.06);
  border-color: rgba(232, 118, 10, 0.2);
}

.topic-card h4 {
  color: var(--color-primary-light);
  font-size: 1rem;
  margin-bottom: 14px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--color-border);
}

.topic-card ul li {
  position: relative;
  padding: 4px 0 4px 18px;
  font-size: 0.875rem;
  color: var(--color-text-muted);
}

.topic-card ul li::before {
  content: "▸";
  position: absolute;
  left: 0;
  color: var(--color-primary);
  font-size: 0.75rem;
}

/* ===== Resources ===== */
.resource-category {
  margin-bottom: 64px;
}

.category-title {
  font-size: 1.75rem;
  color: #fff;
  margin-bottom: 32px;
  padding-bottom: 16px;
  border-bottom: 2px solid var(--color-border);
}

.resource-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 24px;
}

.resource-card {
  padding: 28px;
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  transition: all var(--transition);
  position: relative;
}

.resource-card:hover {
  transform: translateY(-3px);
  border-color: rgba(232, 118, 10, 0.3);
  box-shadow: var(--shadow);
}

.resource-level {
  display: inline-block;
  padding: 4px 12px;
  background: rgba(56, 189, 248, 0.15);
  color: var(--color-accent);
  font-size: 0.75rem;
  font-weight: 600;
  border-radius: 12px;
  margin-bottom: 14px;
}

.resource-card h3 {
  font-size: 1.125rem;
  color: #fff;
  margin-bottom: 10px;
}

.resource-card p {
  font-size: 0.875rem;
  color: var(--color-text-muted);
}

.resource-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.resource-link {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 20px 24px;
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  color: var(--color-text);
  transition: all var(--transition);
}

.resource-link:hover {
  border-color: var(--color-primary);
  background: rgba(232, 118, 10, 0.06);
  color: #fff;
  transform: translateX(4px);
}

.link-icon {
  font-size: 1.25rem;
  flex-shrink: 0;
}

.resource-link strong {
  display: block;
  font-size: 1rem;
  margin-bottom: 4px;
}

.resource-link p {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  margin: 0;
}

/* ===== About Page ===== */
.about-block {
  margin-bottom: 48px;
}

.about-block h2 {
  font-size: 1.5rem;
  color: #fff;
  margin-bottom: 20px;
  padding-bottom: 12px;
  border-bottom: 2px solid var(--color-primary);
  display: inline-block;
}

.about-block p {
  color: var(--color-text-muted);
  margin-bottom: 16px;
  line-height: 1.8;
}

.info-table {
  width: 100%;
  border-collapse: collapse;
  background: var(--color-bg-card);
  border-radius: var(--radius);
  overflow: hidden;
  border: 1px solid var(--color-border);
}

.info-table th,
.info-table td {
  padding: 16px 24px;
  text-align: left;
  border-bottom: 1px solid var(--color-border);
  font-size: 0.9375rem;
}

.info-table tr:last-child th,
.info-table tr:last-child td {
  border-bottom: none;
}

.info-table th {
  width: 160px;
  background: rgba(255, 255, 255, 0.03);
  color: var(--color-text-muted);
  font-weight: 500;
  white-space: nowrap;
}

.info-table td {
  color: var(--color-text);
}

.info-table td a {
  color: var(--color-accent);
}

/* ===== Footer ===== */
.footer {
  background: var(--color-bg-dark);
  border-top: 1px solid var(--color-border);
  padding: 64px 0 32px;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr;
  gap: 48px;
  margin-bottom: 48px;
}

.footer-brand p {
  color: var(--color-text-muted);
  font-size: 0.875rem;
  margin-top: 16px;
  max-width: 320px;
}

.footer-links h4 {
  color: #fff;
  font-size: 1rem;
  margin-bottom: 20px;
}

.footer-links ul li {
  margin-bottom: 10px;
}

.footer-links ul li,
.footer-links ul li a {
  font-size: 0.875rem;
  color: var(--color-text-muted);
}

.footer-links ul li a:hover {
  color: var(--color-primary-light);
}

.footer-bottom {
  padding-top: 32px;
  border-top: 1px solid var(--color-border);
  text-align: center;
}

.footer-bottom p {
  font-size: 0.8125rem;
  color: var(--color-text-dim);
  margin-bottom: 8px;
}

.footer-bottom a {
  color: var(--color-text-dim);
}

.footer-bottom a:hover {
  color: var(--color-text-muted);
}

/* ===== Animations ===== */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(24px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes bounce {
  0%, 100% { transform: rotate(45deg) translateY(0); }
  50% { transform: rotate(45deg) translateY(6px); }
}

.fade-in {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .section {
    padding: 64px 0;
  }

  .section-title {
    font-size: 1.875rem;
  }

  .nav-toggle {
    display: flex;
  }

  .nav-menu {
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    background: rgba(2, 6, 23, 0.98);
    flex-direction: column;
    padding: 16px;
    gap: 4px;
    border-bottom: 1px solid var(--color-border);
    transform: translateY(-120%);
    opacity: 0;
    transition: all var(--transition);
    pointer-events: none;
  }

  .nav-menu.open {
    transform: translateY(0);
    opacity: 1;
    pointer-events: all;
  }

  .nav-menu a {
    padding: 14px 20px;
  }

  .hero-stats {
    gap: 32px;
  }

  .stat-num {
    font-size: 2rem;
  }

  .footer-grid {
    grid-template-columns: 1fr;
    gap: 32px;
  }

  .stage-header {
    padding: 20px;
  }

  .stage-body {
    padding: 20px;
  }

  .page-hero h1 {
    font-size: 2rem;
  }

  .info-table th {
    width: 100px;
    font-size: 0.8125rem;
  }

  .info-table th,
  .info-table td {
    padding: 12px 16px;
  }
}

@media (max-width: 480px) {
  .hero-actions {
    flex-direction: column;
    align-items: center;
  }

  .btn {
    width: 100%;
    max-width: 280px;
  }

  .hero-stats {
    flex-direction: column;
    gap: 24px;
  }
}