:root {
  --color-primary: #FF6B35;
  --color-primary-dark: #E55A2B;
  --color-primary-light: #FF8F66;
  --color-secondary: #F7C948;
  --color-secondary-dark: #E5B830;
  --color-bg: #FFFFFF;
  --color-bg-light: #FFF9F5;
  --color-bg-gray: #F5F5F5;
  --color-text: #333333;
  --color-text-secondary: #666666;
  --color-text-light: #999999;
  --color-border: #E0E0E0;
  --color-danger: #E74C3C;
  --color-success: #27AE60;
  --color-info: #3498DB;
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.08);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.12);
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --max-width: 1200px;
  --header-height: 70px;
  --transition: 0.3s ease;
}

body {
  font-family: "PingFang SC", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  color: var(--color-text);
  background-color: var(--color-bg);
  min-height: 100vh;
}

.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 20px;
}

main {
  min-height: calc(100vh - var(--header-height) - 300px);
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 10px 24px;
  border-radius: var(--radius-sm);
  font-size: 14px;
  font-weight: 500;
  transition: all var(--transition);
  cursor: pointer;
}

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

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

.btn-secondary {
  background: var(--color-secondary);
  color: var(--color-text);
}

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

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

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

.btn-lg {
  padding: 14px 36px;
  font-size: 16px;
}

.btn-sm {
  padding: 6px 16px;
  font-size: 13px;
}

.section {
  padding: 60px 0;
}

.section-title {
  text-align: center;
  margin-bottom: 40px;
}

.section-title h2 {
  font-size: 28px;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 12px;
}

.section-title p {
  font-size: 16px;
  color: var(--color-text-secondary);
}

.text-primary { color: var(--color-primary); }
.text-secondary { color: var(--color-text-secondary); }
.text-light { color: var(--color-text-light); }

.back-to-top {
  position: fixed;
  bottom: 30px;
  right: 30px;
  width: 44px;
  height: 44px;
  background: var(--color-primary);
  color: #fff;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 20px;
  cursor: pointer;
  opacity: 0;
  transform: translateY(20px);
  transition: all var(--transition);
  z-index: 999;
  box-shadow: var(--shadow-md);
  border: none;
}

.back-to-top.visible {
  opacity: 1;
  transform: translateY(0);
}

.back-to-top:hover {
  background: var(--color-primary-dark);
}

@media (max-width: 768px) {
  :root {
    --header-height: 60px;
  }
  .section {
    padding: 40px 0;
  }
  .section-title h2 {
    font-size: 22px;
  }
  .btn-lg {
    padding: 12px 28px;
    font-size: 15px;
  }
  .back-to-top {
    width: 38px;
    height: 38px;
    font-size: 16px;
    bottom: 20px;
    right: 20px;
  }
}