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

:root {
  --primary: #0891b2;
  --primary-dark: #0e7490;
  --primary-hover: #155e75;
  --accent: #06b6d4;
  --bg: #f8fafc;
  --bg-alt: #f0f9ff;
  --card: #ffffff;
  --text: #1e293b;
  --text-secondary: #475569;
  --text-muted: #94a3b8;
  --border: #e2e8f0;
  --star: #f59e0b;
  --radius: 12px;
  --radius-sm: 8px;
  --shadow: 0 1px 3px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
  --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.07), 0 2px 4px -2px rgba(0,0,0,0.04);
  --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.08), 0 4px 6px -4px rgba(0,0,0,0.03);
  --transition: 0.2s ease;
}

html { scroll-behavior: smooth; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans SC", sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--primary); text-decoration: none; transition: color var(--transition); }
a:hover { color: var(--primary-dark); }
img { max-width: 100%; height: auto; }

.container {
  max-width: 1120px;
  margin: 0 auto;
  padding: 0 24px;
}

/* ===== Header ===== */
.header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255,255,255,0.92);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}

.header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 60px;
}

.header-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 17px;
  font-weight: 700;
  color: var(--text);
}

.header-logo:hover { color: var(--text); }

.header-logo img {
  width: 28px;
  height: 28px;
  border-radius: 6px;
}

.header-nav {
  display: flex;
  gap: 28px;
  list-style: none;
}

.header-nav a {
  color: var(--text-secondary);
  font-size: 15px;
  font-weight: 500;
  padding: 6px 0;
  transition: color var(--transition);
}

.header-nav a:hover,
.header-nav a.active {
  color: var(--primary);
}

/* ===== Hero ===== */
.hero {
  background: linear-gradient(135deg, #0c4a6e 0%, #164e63 50%, #134e4a 100%);
  color: #fff;
  padding: 80px 0 72px;
  text-align: center;
}

.hero h1 {
  font-size: 44px;
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 16px;
  letter-spacing: -0.02em;
}

.hero .subtitle {
  font-size: 18px;
  color: rgba(255,255,255,0.72);
  max-width: 560px;
  margin: 0 auto 40px;
  line-height: 1.7;
}

.hero-buttons {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 12px;
}

.hero-hint {
  display: block;
  color: rgba(255,255,255,0.4);
  font-size: 13px;
  margin-top: 14px;
}

/* ===== Buttons ===== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 14px 28px;
  font-size: 16px;
  font-weight: 600;
  border-radius: var(--radius-sm);
  border: none;
  cursor: pointer;
  transition: all var(--transition);
  text-decoration: none;
  line-height: 1;
}

.btn-primary {
  background: var(--primary);
  color: #fff;
}

.btn-primary:hover {
  background: var(--primary-hover);
  color: #fff;
  transform: translateY(-1px);
  box-shadow: 0 4px 14px rgba(8,145,178,0.35);
}

.btn-secondary {
  background: rgba(255,255,255,0.1);
  color: #fff;
  border: 1px solid rgba(255,255,255,0.22);
}

.btn-secondary:hover {
  background: rgba(255,255,255,0.18);
  color: #fff;
}

.btn-outline {
  background: transparent;
  color: var(--primary);
  border: 2px solid var(--primary);
}

.btn-outline:hover {
  background: var(--primary);
  color: #fff;
}

.btn-sm {
  padding: 10px 20px;
  font-size: 14px;
}

.btn-hint {
  display: block;
  font-size: 12px;
  color: var(--text-muted);
  margin-top: 6px;
  text-align: center;
}

/* ===== Sections ===== */
.section {
  padding: 68px 0;
}

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

.section-title {
  font-size: 28px;
  font-weight: 700;
  text-align: center;
  margin-bottom: 44px;
  color: var(--text);
}

/* ===== Review Cards ===== */
.reviews-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.review-card {
  background: var(--card);
  border-radius: var(--radius);
  padding: 28px;
  box-shadow: var(--shadow);
  transition: box-shadow var(--transition);
}

.review-card:hover {
  box-shadow: var(--shadow-md);
}

.review-stars {
  color: var(--star);
  font-size: 18px;
  margin-bottom: 14px;
  letter-spacing: 2px;
}

.review-text {
  font-size: 15px;
  color: var(--text-secondary);
  line-height: 1.7;
  margin-bottom: 20px;
}

.review-user {
  display: flex;
  align-items: center;
  gap: 12px;
}

.review-avatar {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  object-fit: cover;
}

.review-name {
  font-size: 14px;
  font-weight: 600;
  color: var(--text);
}

.review-meta {
  font-size: 12px;
  color: var(--text-muted);
}

/* ===== Knowledge Cards ===== */
.knowledge-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
}

.knowledge-card {
  background: var(--card);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow);
  transition: box-shadow var(--transition), transform var(--transition);
}

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

.knowledge-card h3 {
  font-size: 16px;
  font-weight: 600;
  margin-bottom: 10px;
  color: var(--text);
  line-height: 1.4;
}

.knowledge-card p {
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.7;
}

/* ===== Platform Cards ===== */
.platform-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.platform-card {
  background: var(--card);
  border-radius: var(--radius);
  padding: 32px 28px;
  box-shadow: var(--shadow);
  transition: box-shadow var(--transition);
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
}

.platform-card:hover {
  box-shadow: var(--shadow-md);
}

.platform-name {
  font-size: 20px;
  font-weight: 700;
  margin-bottom: 8px;
  color: var(--text);
}

.platform-version {
  font-size: 13px;
  color: var(--text-muted);
  margin-bottom: 4px;
}

.platform-req {
  font-size: 13px;
  color: var(--text-secondary);
  margin-bottom: 24px;
}

.platform-card .btn {
  width: 100%;
  margin-bottom: 6px;
}

.platform-variants {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  justify-content: center;
  margin-top: 8px;
}

.platform-variants a {
  font-size: 13px;
  color: var(--primary);
  padding: 4px 10px;
  border-radius: 4px;
  transition: background var(--transition);
}

.platform-variants a:hover {
  background: rgba(8,145,178,0.06);
}

.variant-sep {
  color: var(--border);
  line-height: 28px;
}

/* ===== Version Channels ===== */
.channels {
  display: flex;
  justify-content: center;
  gap: 20px;
  margin-top: 56px;
  padding-top: 56px;
  border-top: 1px solid var(--border);
}

.channel-card {
  background: var(--card);
  border-radius: var(--radius);
  padding: 28px 32px;
  box-shadow: var(--shadow);
  text-align: center;
  min-width: 200px;
  transition: box-shadow var(--transition);
}

.channel-card:hover {
  box-shadow: var(--shadow-md);
}

.channel-card .label {
  font-size: 16px;
  font-weight: 600;
  margin-bottom: 6px;
  color: var(--text);
}

.channel-card .desc {
  font-size: 13px;
  color: var(--text-muted);
  margin-bottom: 16px;
  line-height: 1.5;
}

.channel-card.recommended {
  border: 2px solid var(--primary);
}

.channel-badge {
  display: inline-block;
  background: var(--primary);
  color: #fff;
  font-size: 11px;
  font-weight: 600;
  padding: 2px 10px;
  border-radius: 10px;
  margin-bottom: 10px;
}

/* ===== Download Hero ===== */
.download-hero {
  background: linear-gradient(135deg, #0c4a6e 0%, #164e63 50%, #134e4a 100%);
  color: #fff;
  padding: 56px 0 48px;
  text-align: center;
}

.download-hero h1 {
  font-size: 38px;
  font-weight: 800;
  margin-bottom: 12px;
  letter-spacing: -0.02em;
}

.download-hero .subtitle {
  font-size: 17px;
  color: rgba(255,255,255,0.65);
}

/* ===== Footer ===== */
.footer {
  background: #0c4a6e;
  color: rgba(255,255,255,0.5);
  padding: 44px 0;
  font-size: 13px;
  line-height: 1.9;
  text-align: center;
}

.footer p { margin-bottom: 2px; }

.footer .copyright {
  margin-top: 18px;
  color: rgba(255,255,255,0.25);
}

/* ===== Responsive ===== */
@media (max-width: 1024px) {
  .knowledge-grid { grid-template-columns: repeat(2, 1fr); }
  .platform-grid { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 768px) {
  .hero { padding: 60px 0 52px; }
  .hero h1 { font-size: 30px; }
  .hero .subtitle { font-size: 16px; margin-bottom: 32px; }
  .hero-buttons { flex-direction: column; align-items: center; }
  .hero-buttons .btn { width: 260px; }

  .section { padding: 48px 0; }
  .section-title { font-size: 24px; margin-bottom: 28px; }

  .reviews-grid { grid-template-columns: 1fr; }
  .knowledge-grid { grid-template-columns: 1fr; }
  .platform-grid { grid-template-columns: 1fr; max-width: 420px; margin: 0 auto; }

  .channels { flex-direction: column; align-items: center; }
  .channel-card { width: 100%; max-width: 320px; }

  .download-hero { padding: 44px 0 36px; }
  .download-hero h1 { font-size: 28px; }
}

@media (max-width: 480px) {
  .hero h1 { font-size: 26px; }
  .container { padding: 0 16px; }
  .btn { padding: 12px 24px; font-size: 15px; }
  .review-card { padding: 22px; }
  .knowledge-card { padding: 20px; }
}