:root {
  --primary-color: #4285f4;
  --secondary-color: #20c997;
  --text-color: #333;
  --bg-color: #fff;
  --light-bg: #f8f9fa;
  --border-color: #ddd;
  --shadow: 0 4px 12px rgba(0,0,0,0.08);
  --transition: all 0.3s ease;
}

/* Mobile-first styles */
.epub-hero {
  text-align: center;
  padding: 2rem 1rem;
  background-color: var(--light-bg);
  border-radius: 0.75rem;
  margin-bottom: 1.5rem;
}

.epub-hero h1 {
  font-size: 1.75rem;
  font-weight: 700;
  margin-bottom: 0.75rem;
  line-height: 1.3;
}

.epub-hero p {
  font-size: 1rem;
  color: #6c757d;
  margin-bottom: 1.5rem;
  max-width: 800px;
  margin-left: auto;
  margin-right: auto;
  line-height: 1.6;
}

.upload-card {
  background-color: var(--bg-color);
  border: 2px dashed var(--border-color);
  border-radius: 1rem;
  padding: 1.5rem 1rem;
  text-align: center;
  margin-bottom: 1.5rem;
  cursor: pointer;
  transition: var(--transition);
}

.upload-card:hover {
  border-color: var(--secondary-color);
  background-color: rgba(32, 201, 151, 0.02);
}

.upload-icon {
  font-size: 2.5rem;
  color: var(--secondary-color);
  margin-bottom: 1rem;
}

.epub-btn {
  background-color: var(--secondary-color);
  border-color: var(--secondary-color);
  border-radius: 0.5rem;
  padding: 0.5rem 1rem;
  font-weight: 500;
  font-size: 0.9rem;
  transition: var(--transition);
}

.epub-btn:hover {
  background-color: #1ba87e;
  border-color: #1ba87e;
  transform: translateY(-2px);
  box-shadow: 0 4px 8px rgba(0,0,0,0.1);
}

.features-section {
  margin-bottom: 2.5rem;
}

.feature-card {
  background-color: var(--bg-color);
  border-radius: 0.75rem;
  padding: 1.25rem;
  height: 100%;
  box-shadow: var(--shadow);
  transition: var(--transition);
  margin-bottom: 1rem;
}

.feature-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 8px 16px rgba(0,0,0,0.1);
}

.feature-icon {
  font-size: 1.75rem;
  color: var(--secondary-color);
  margin-bottom: 0.75rem;
}

.feature-card h3 {
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
}

.feature-card p {
  font-size: 0.9rem;
  color: #6c757d;
  line-height: 1.5;
}

.epub-example {
  background-color: var(--bg-color);
  border-radius: 0.75rem;
  padding: 1.25rem;
  margin-bottom: 2rem;
  box-shadow: var(--shadow);
}

.book-preview {
  border: 1px solid var(--border-color);
  border-radius: 0.75rem;
  overflow: hidden;
  box-shadow: var(--shadow);
  margin-bottom: 1.5rem;
}

.book-cover {
  max-width: 150px;
  margin: 0 auto;
  display: block;
}

.book-pages {
  background-color: var(--bg-color);
  padding: 1.5rem;
  border-radius: 0 0 0.75rem 0.75rem;
  min-height: 200px;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  font-style: italic;
  color: #6c757d;
}

.info-card {
  background-color: var(--bg-color);
  border-radius: 0.75rem;
  padding: 1.25rem;
  height: 100%;
  box-shadow: var(--shadow);
  margin-bottom: 1rem;
}

.info-card h3 {
  font-size: 1.25rem;
  margin-bottom: 0.75rem;
  display: flex;
  align-items: center;
  font-weight: 600;
}

.info-card h3 i {
  margin-right: 0.5rem;
}

.info-card p {
  margin-bottom: 0.75rem;
  font-size: 0.9rem;
  line-height: 1.6;
}

.info-card ul {
  padding-left: 1.5rem;
  margin-bottom: 0;
}

.info-card li {
  margin-bottom: 0.25rem;
  font-size: 0.9rem;
}

.mobile-demo {
  position: relative;
  width: 280px;
  margin: 0 auto;
  border-radius: 1.5rem;
  overflow: hidden;
  box-shadow: 0 12px 24px rgba(0,0,0,0.15);
  border: 8px solid #333;
}

.mobile-header {
  background-color: #333;
  color: white;
  padding: 0.5rem;
  text-align: center;
  font-size: 0.75rem;
}

.mobile-screen {
  background-color: #fff;
  padding: 0.75rem;
  height: 450px;
  overflow: hidden;
}

.mobile-toolbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-bottom: 1px solid #eee;
  padding-bottom: 0.5rem;
  margin-bottom: 0.75rem;
  font-size: 0.75rem;
}

.mobile-content {
  font-size: 0.75rem;
  line-height: 1.5;
  overflow: hidden;
  height: 350px;
}

/* Tablet and desktop styles */
@media (min-width: 768px) {
  .epub-hero {
    padding: 3rem 2rem;
    margin-bottom: 2.5rem;
  }
  
  .epub-hero h1 {
    font-size: 2.25rem;
  }
  
  .epub-hero p {
    font-size: 1.1rem;
  }
  
  .upload-card {
    padding: 2.5rem;
  }
  
  .upload-icon {
    font-size: 3rem;
  }
  
  .feature-card {
    margin-bottom: 0;
  }
  
  .info-card {
    margin-bottom: 0;
  }
  
  .mobile-demo {
    width: 320px;
  }
}