/* ===== 全局变量 ===== */
:root {
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --primary-light: #60a5fa;
  --accent: #f97316;
  --text: #1f2937;
  --text-light: #4b5563;
  --text-lighter: #9ca3af;
  --bg: #ffffff;
  --bg-light: #f9fafb;
  --border: #e5e7eb;
  --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  --radius: 8px;
  --radius-lg: 12px;
  --transition: all 0.2s ease;
  --container: 1200px;
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
}

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

body {
  font-family: var(--font-sans);
  color: var(--text);
  line-height: 1.6;
  background: var(--bg);
}

.container {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 24px;
}

a {
  text-decoration: none;
  color: inherit;
}

ul {
  list-style: none;
}

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

/* ===== 按钮 ===== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 20px;
  border-radius: var(--radius);
  font-weight: 500;
  font-size: 16px;
  transition: var(--transition);
  cursor: pointer;
  border: none;
  white-space: nowrap;
}

.btn-primary {
  background: var(--primary);
  color: white;
}
.btn-primary:hover {
  background: var(--primary-dark);
}

.btn-outline {
  background: transparent;
  color: var(--primary);
  border: 1px solid var(--primary);
}
.btn-outline:hover {
  background: var(--primary);
  color: white;
}

.btn-large {
  padding: 14px 28px;
  font-size: 18px;
}

/* ===== 导航栏 ===== */
.navbar {
  position: sticky;
  top: 0;
  background: rgba(255,255,255,0.9);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border);
  z-index: 100;
  height: 70px;
}
.navbar .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}
.logo {
  display: flex;
  align-items: center;
  gap: 8px;
  font-weight: 600;
  font-size: 20px;
  color: var(--primary);
}
.logo-icon {
  background: var(--primary);
  color: white;
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius);
  font-size: 18px;
}
.nav-links {
  display: flex;
  gap: 32px;
}
.nav-links a {
  font-weight: 500;
  color: var(--text-light);
  transition: color 0.2s;
}
.nav-links a:hover,
.nav-links a.active {
  color: var(--primary);
}
.menu-toggle {
  display: none;
  background: none;
  border: none;
  font-size: 24px;
  color: var(--text);
  cursor: pointer;
}
@media (max-width: 768px) {
  .nav-links {
    position: absolute;
    top: 70px;
    left: 0;
    width: 100%;
    background: white;
    flex-direction: column;
    align-items: center;
    padding: 20px;
    gap: 20px;
    border-bottom: 1px solid var(--border);
    transform: translateY(-100%);
    opacity: 0;
    transition: all 0.3s;
    pointer-events: none;
  }
  .nav-links.active {
    transform: translateY(0);
    opacity: 1;
    pointer-events: auto;
  }
  .menu-toggle {
    display: block;
  }
}

/* ===== 页脚 ===== */
.footer {
  background: #111827;
  color: #9ca3af;
  padding: 48px 0 24px;
}
.footer-content {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 40px;
  margin-bottom: 40px;
}
.footer-column h4 {
  color: white;
  margin-bottom: 20px;
  font-size: 16px;
  font-weight: 600;
}
.footer-column ul li {
  margin-bottom: 8px;
}
.footer-column a {
  color: #9ca3af;
  font-size: 14px;
  transition: color 0.2s;
}
.footer-column a:hover {
  color: white;
}
.footer-bottom {
  text-align: center;
  padding-top: 24px;
  border-top: 1px solid #1f2937;
  font-size: 14px;
}
@media (max-width: 768px) {
  .footer-content {
    grid-template-columns: 1fr 1fr;
  }
}
@media (max-width: 480px) {
  .footer-content {
    grid-template-columns: 1fr;
  }
}

/* ===== 通用标题区 ===== */
.section-header {
  text-align: center;
  margin-bottom: 48px;
}
.section-title {
  font-size: 32px;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 12px;
}
.section-subtitle {
  font-size: 18px;
  color: var(--text-light);
  max-width: 600px;
  margin: 0 auto;
}

/* ===== 卡片网格 ===== */
.grid-3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 30px;
}
@media (max-width: 992px) {
  .grid-3 {
    grid-template-columns: repeat(2, 1fr);
  }
}
@media (max-width: 640px) {
  .grid-3 {
    grid-template-columns: 1fr;
  }
}

.card {
  background: white;
  border-radius: var(--radius-lg);
  padding: 32px 24px;
  box-shadow: var(--shadow);
  transition: var(--transition);
  border: 1px solid var(--border);
}
.card:hover {
  box-shadow: var(--shadow-lg);
}

.feature-icon {
  width: 56px;
  height: 56px;
  background: rgba(37, 99, 235, 0.1);
  border-radius: var(--radius);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 20px;
  color: var(--primary);
  font-size: 24px;
}
.card h3 {
  font-size: 20px;
  margin-bottom: 12px;
  font-weight: 600;
}
.card p {
  color: var(--text-light);
  font-size: 15px;
  line-height: 1.5;
}

/* ===== 平台卡片 ===== */
.platform-grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 20px;
  margin-top: 40px;
}
@media (max-width: 768px) {
  .platform-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}
@media (max-width: 480px) {
  .platform-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}
.platform-card {
  background: var(--bg-light);
  border-radius: var(--radius);
  padding: 24px 16px;
  text-align: center;
  transition: var(--transition);
  border: 1px solid transparent;
}
.platform-card:hover {
  border-color: var(--primary);
  transform: translateY(-2px);
}
.platform-card i {
  font-size: 40px;
  color: var(--primary);
  margin-bottom: 12px;
}
.platform-card h4 {
  font-size: 16px;
  font-weight: 500;
  color: var(--text);
}

/* ===== 下载卡片 ===== */
.download-grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 20px;
  margin: 40px 0;
}
@media (max-width: 992px) {
  .download-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}
@media (max-width: 640px) {
  .download-grid {
    grid-template-columns: 1fr;
  }
}
.download-card {
  background: white;
  border-radius: var(--radius-lg);
  padding: 24px;
  text-align: center;
  box-shadow: var(--shadow);
  transition: var(--transition);
  border: 1px solid var(--border);
  position: relative;
}
.download-card.featured {
  border-color: var(--primary);
}
.download-badge {
  position: absolute;
  top: -10px;
  right: 16px;
  background: var(--accent);
  color: white;
  padding: 4px 12px;
  border-radius: 20px;
  font-size: 12px;
  font-weight: 600;
}
.download-card i {
  font-size: 48px;
  color: var(--primary);
  margin-bottom: 12px;
}
.download-card h3 {
  font-size: 20px;
  margin-bottom: 4px;
}
.version {
  font-size: 14px;
  color: var(--text-light);
  margin-bottom: 16px;
}
.download-card p {
  font-size: 14px;
  color: var(--text-light);
  margin-bottom: 20px;
}
.download-card .btn {
  width: 100%;
}

/* ===== 页头 ===== */
.page-header {
  padding: 80px 0 40px;
  background: linear-gradient(to bottom, var(--bg-light), white);
  text-align: center;
}
.page-header h1 {
  font-size: 48px;
  font-weight: 700;
  margin-bottom: 16px;
  color: var(--text);
}
.page-header p {
  font-size: 20px;
  color: var(--text-light);
  max-width: 700px;
  margin: 0 auto;
}

/* ===== 版本信息 ===== */
.version-info {
  display: flex;
  justify-content: center;
  gap: 40px;
  margin-top: 32px;
}
.info-item {
  text-align: center;
}
.info-label {
  font-size: 14px;
  color: var(--text-lighter);
}
.info-value {
  font-size: 20px;
  font-weight: 600;
  color: var(--primary);
}

/* ===== 系统要求 ===== */
.requirements-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
  margin-top: 40px;
}
@media (max-width: 992px) {
  .requirements-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}
@media (max-width: 640px) {
  .requirements-grid {
    grid-template-columns: 1fr;
  }
}
.req-card {
  background: var(--bg-light);
  padding: 24px;
  border-radius: var(--radius);
}
.req-card h4 {
  font-size: 18px;
  margin-bottom: 16px;
  font-weight: 600;
}
.req-card ul {
  list-style: none;
}
.req-card li {
  padding: 4px 0;
  color: var(--text-light);
  font-size: 14px;
}

/* ===== 其他 ===== */
.mt-8 { margin-top: 32px; }
.mb-8 { margin-bottom: 32px; }
.text-center { text-align: center; }