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

:root {
  --c-blue: #4285F4;
  --c-blue-hover: #1967D2;
  --c-green: #34A853;
  --c-yellow: #FBBC04;
  --c-red: #EA4335;
  --c-bg: #F8F9FA;
  --c-white: #FFFFFF;
  --c-text-dark: #202124;
  --c-text-mid: #5F6368;
  --c-text-light: #80868B;
  --c-border: #DADCE0;
  --c-card-hover: #F1F3F4;
  --shadow-sm: 0 2px 8px rgba(60,64,67,0.08), 0 2px 4px rgba(60,64,67,0.04);
  --shadow-md: 0 4px 16px rgba(60,64,67,0.12), 0 2px 8px rgba(60,64,67,0.08);
  --shadow-nav: 0 1px 2px rgba(60,64,67,0.08);
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 24px;
  --max-w: 1200px;
}

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

body {
  font-family: 'PingFang SC', 'Microsoft YaHei', 'Noto Sans SC', 'Roboto', 'Segoe UI', Arial, sans-serif;
  color: var(--c-text-dark);
  background: var(--c-bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--c-blue); text-decoration: none; }
a:hover { text-decoration: underline; }

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

/* ========== Spin Animation ========== */
@keyframes spin {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}

/* ========== Fade In Animation ========== */
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(30px); }
  to { opacity: 1; transform: translateY(0); }
}

.fade-in {
  opacity: 0;
  animation: fadeInUp 0.5s ease-out forwards;
}

/* IntersectionObserver will add .visible class */
.reveal {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.5s ease-out, transform 0.5s ease-out;
}
.reveal.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ========== Container ========== */
.container {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 0 24px;
}

/* ========== Navigation ========== */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 64px;
  background: var(--c-white);
  border-bottom: 1px solid var(--c-border);
  box-shadow: var(--shadow-nav);
  z-index: 1000;
  display: flex;
  align-items: center;
}

.navbar-inner {
  max-width: var(--max-w);
  width: 100%;
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 18px;
  font-weight: 600;
  color: var(--c-text-dark);
}
.logo svg { flex-shrink: 0; }
.logo:hover { text-decoration: none; }

.nav-links {
  display: flex;
  align-items: center;
  gap: 32px;
  list-style: none;
}

.nav-links a {
  font-size: 15px;
  font-weight: 500;
  color: var(--c-text-mid);
  padding: 8px 0;
  position: relative;
  transition: color 0.2s;
}

.nav-links a:hover {
  color: var(--c-blue);
  text-decoration: none;
}

.nav-links a.active {
  color: var(--c-blue);
  font-weight: 600;
}

.nav-links a.active::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  height: 2px;
  background: var(--c-blue);
  border-radius: 1px;
}

/* Mobile nav toggle */
.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

/* ========== Buttons ========== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 32px;
  font-size: 16px;
  font-weight: 500;
  border-radius: var(--radius-lg);
  border: none;
  cursor: pointer;
  transition: all 0.2s ease;
  font-family: inherit;
}

.btn:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

.btn-primary {
  background: var(--c-blue);
  color: var(--c-white);
  box-shadow: 0 2px 4px rgba(66,133,244,0.3);
}

.btn-primary:hover:not(:disabled) {
  background: var(--c-blue-hover);
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(66,133,244,0.4);
  text-decoration: none;
}

.btn-secondary {
  background: var(--c-white);
  color: var(--c-blue);
  border: 1px solid var(--c-border);
}

.btn-secondary:hover:not(:disabled) {
  background: var(--c-card-hover);
  transform: translateY(-1px);
  text-decoration: none;
}

.btn-lg {
  padding: 14px 40px;
  font-size: 17px;
}

.btn-full {
  width: 100%;
}

/* ========== Hero Section ========== */
.hero {
  padding: 140px 0 80px;
  background: linear-gradient(180deg, #E8F0FE 0%, var(--c-bg) 100%);
}

.hero-inner {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 60px;
  align-items: center;
}

.hero-content h1 {
  font-size: 42px;
  font-weight: 700;
  line-height: 1.2;
  margin-bottom: 20px;
  color: var(--c-text-dark);
}

.hero-content .subtitle {
  font-size: 18px;
  color: var(--c-text-mid);
  margin-bottom: 32px;
  line-height: 1.6;
}

.hero-version {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: var(--c-white);
  padding: 6px 16px;
  border-radius: var(--radius-lg);
  font-size: 14px;
  color: var(--c-text-mid);
  margin-bottom: 24px;
  border: 1px solid var(--c-border);
}

.hero-version .dot {
  width: 8px;
  height: 8px;
  background: var(--c-green);
  border-radius: 50%;
  flex-shrink: 0;
}

.hero-actions {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
}

.hero-image {
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: var(--shadow-md);
}

.hero-image img {
  width: 100%;
  display: block;
}

/* ========== Section Base ========== */
.section {
  padding: 80px 0;
}

.section-title {
  font-size: 32px;
  font-weight: 600;
  text-align: center;
  margin-bottom: 16px;
  color: var(--c-text-dark);
}

.section-desc {
  text-align: center;
  font-size: 16px;
  color: var(--c-text-mid);
  max-width: 640px;
  margin: 0 auto 48px;
}

/* ========== Feature Cards ========== */
.features-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
}

.feature-card {
  background: var(--c-white);
  border-radius: var(--radius-md);
  padding: 32px 24px;
  box-shadow: var(--shadow-sm);
  transition: all 0.25s ease;
}

.feature-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.feature-icon {
  width: 56px;
  height: 56px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 20px;
}

.feature-icon.blue { background: #E8F0FE; color: var(--c-blue); }
.feature-icon.green { background: #E6F4EA; color: var(--c-green); }
.feature-icon.yellow { background: #FEF7E0; color: #B06000; }
.feature-icon.red { background: #FCE8E6; color: var(--c-red); }

.feature-card h3 {
  font-size: 20px;
  font-weight: 600;
  margin-bottom: 10px;
  color: var(--c-text-dark);
}

.feature-card p {
  font-size: 15px;
  color: var(--c-text-mid);
  line-height: 1.6;
}

/* ========== Platform Cards ========== */
.platforms-grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 20px;
}

.platform-card {
  background: var(--c-white);
  border-radius: var(--radius-md);
  padding: 28px 20px;
  box-shadow: var(--shadow-sm);
  text-align: center;
  transition: all 0.25s ease;
}

.platform-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.platform-icon {
  margin-bottom: 16px;
  color: var(--c-blue);
}

.platform-card h4 {
  font-size: 18px;
  font-weight: 600;
  margin-bottom: 8px;
}

.platform-card p {
  font-size: 14px;
  color: var(--c-text-mid);
  margin-bottom: 16px;
}

/* ========== Version Table ========== */
.version-table-wrap {
  background: var(--c-white);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  overflow: hidden;
}

.version-table {
  width: 100%;
  border-collapse: collapse;
}

.version-table th,
.version-table td {
  padding: 16px 20px;
  text-align: left;
  font-size: 15px;
}

.version-table th {
  background: var(--c-bg);
  font-weight: 600;
  color: var(--c-text-dark);
  border-bottom: 1px solid var(--c-border);
}

.version-table td {
  color: var(--c-text-mid);
  border-bottom: 1px solid var(--c-border);
}

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

.version-table .tag {
  display: inline-block;
  padding: 4px 12px;
  border-radius: 12px;
  font-size: 13px;
  font-weight: 500;
}

.tag-stable { background: #E6F4EA; color: var(--c-green); }
.tag-beta { background: #FEF7E0; color: #B06000; }
.tag-dev { background: #E8F0FE; color: var(--c-blue); }
.tag-canary { background: #FCE8E6; color: var(--c-red); }

/* ========== FAQ ========== */
.faq-list {
  max-width: 800px;
  margin: 0 auto;
}

.faq-item {
  background: var(--c-white);
  border-radius: var(--radius-md);
  margin-bottom: 12px;
  box-shadow: var(--shadow-sm);
  overflow: hidden;
}

.faq-question {
  width: 100%;
  padding: 20px 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: none;
  border: none;
  font-size: 16px;
  font-weight: 500;
  color: var(--c-text-dark);
  cursor: pointer;
  text-align: left;
  font-family: inherit;
}

.faq-question:hover {
  background: var(--c-card-hover);
}

.faq-question .chevron {
  transition: transform 0.3s ease;
  flex-shrink: 0;
  color: var(--c-text-light);
}

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

.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease, padding 0.3s ease;
}

.faq-item.open .faq-answer {
  max-height: 500px;
  padding: 0 24px 20px;
}

.faq-answer p {
  font-size: 15px;
  color: var(--c-text-mid);
  line-height: 1.7;
}

/* ========== Download Section Layouts ========== */
.download-section {
  background: var(--c-white);
  border-radius: var(--radius-md);
  padding: 40px;
  box-shadow: var(--shadow-sm);
  margin-bottom: 24px;
}

.download-section h2 {
  font-size: 24px;
  font-weight: 600;
  margin-bottom: 8px;
}

.download-section .section-note {
  font-size: 15px;
  color: var(--c-text-mid);
  margin-bottom: 28px;
}

.download-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
}

.download-card {
  background: var(--c-bg);
  border-radius: var(--radius-md);
  padding: 28px;
  text-align: center;
}

.download-card .os-icon {
  margin-bottom: 16px;
  color: var(--c-blue);
}

.download-card h4 {
  font-size: 18px;
  font-weight: 600;
  margin-bottom: 8px;
}

.download-card p {
  font-size: 14px;
  color: var(--c-text-mid);
  margin-bottom: 20px;
}

/* ========== Install Steps ========== */
.steps-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.step-card {
  background: var(--c-white);
  border-radius: var(--radius-md);
  padding: 32px;
  box-shadow: var(--shadow-sm);
  text-align: center;
}

.step-number {
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--c-blue);
  color: var(--c-white);
  font-size: 20px;
  font-weight: 600;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 20px;
}

.step-card h4 {
  font-size: 18px;
  font-weight: 600;
  margin-bottom: 12px;
}

.step-card p {
  font-size: 15px;
  color: var(--c-text-mid);
  line-height: 1.6;
}

/* ========== Guide Content ========== */
.guide-content {
  background: var(--c-white);
  border-radius: var(--radius-md);
  padding: 40px;
  box-shadow: var(--shadow-sm);
}

.guide-content h2 {
  font-size: 24px;
  font-weight: 600;
  margin-bottom: 20px;
}

.guide-content h3 {
  font-size: 20px;
  font-weight: 600;
  margin: 32px 0 12px;
  color: var(--c-text-dark);
}

.guide-content p {
  font-size: 16px;
  color: var(--c-text-mid);
  line-height: 1.8;
  margin-bottom: 16px;
}

.guide-content ol,
.guide-content ul {
  margin: 16px 0 16px 24px;
  color: var(--c-text-mid);
  line-height: 1.8;
}

.guide-content li {
  margin-bottom: 8px;
}

.guide-content strong {
  color: var(--c-text-dark);
  font-weight: 600;
}

.guide-tip {
  background: #E8F0FE;
  border-left: 4px solid var(--c-blue);
  padding: 16px 20px;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  margin: 20px 0;
}

.guide-tip p {
  margin: 0;
  color: var(--c-blue-hover);
  font-size: 15px;
}

/* ========== Footer ========== */
.footer {
  background: var(--c-bg);
  border-top: 1px solid var(--c-border);
  padding: 40px 0 32px;
  margin-top: 60px;
}

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

.footer-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  color: var(--c-green);
  font-size: 14px;
  font-weight: 500;
  margin-bottom: 16px;
}

.footer-copy {
  font-size: 14px;
  color: var(--c-text-light);
}

/* ========== Breadcrumb ========== */
.breadcrumb {
  padding: 24px 0 0;
  font-size: 14px;
  color: var(--c-text-light);
}

.breadcrumb a { color: var(--c-text-mid); }
.breadcrumb a:hover { color: var(--c-blue); }
.breadcrumb .sep { margin: 0 8px; }

/* ========== Responsive ========== */
@media (max-width: 1024px) {
  .features-grid { grid-template-columns: repeat(2, 1fr); }
  .platforms-grid { grid-template-columns: repeat(3, 1fr); }
  .download-grid { grid-template-columns: repeat(2, 1fr); }
  .steps-grid { grid-template-columns: repeat(2, 1fr); }
  .hero-inner { gap: 40px; }
  .hero-content h1 { font-size: 36px; }
}

@media (max-width: 768px) {
  .nav-links {
    display: none;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--c-white);
    flex-direction: column;
    padding: 16px 24px;
    gap: 0;
    border-bottom: 1px solid var(--c-border);
    box-shadow: var(--shadow-md);
  }
  .nav-links.show { display: flex; }
  .nav-links a {
    padding: 12px 0;
    border-bottom: 1px solid var(--c-border);
  }
  .nav-links a:last-child { border-bottom: none; }
  .nav-links a.active::after { display: none; }
  .nav-links a.active { background: var(--c-bg); margin: 0 -24px; padding: 12px 24px; }
  .nav-toggle { display: block; }

  .hero { padding: 100px 0 60px; }
  .hero-inner { grid-template-columns: 1fr; }
  .hero-content h1 { font-size: 28px; }
  .hero-content .subtitle { font-size: 16px; }
  .hero-actions { flex-direction: column; }
  .hero-actions .btn { width: 100%; }
  .hero-image { order: -1; }

  .section { padding: 60px 0; }
  .section-title { font-size: 26px; }

  .features-grid { grid-template-columns: 1fr; }
  .platforms-grid { grid-template-columns: repeat(2, 1fr); }
  .download-grid { grid-template-columns: 1fr; }
  .steps-grid { grid-template-columns: 1fr; }

  .download-section { padding: 28px; }
  .guide-content { padding: 28px; }

  .version-table th,
  .version-table td { padding: 12px 14px; font-size: 14px; }
}

@media (max-width: 480px) {
  .platforms-grid { grid-template-columns: 1fr; }
  .hero-content h1 { font-size: 24px; }
  .section-title { font-size: 22px; }
}