:root {
  --primary-color: #2c3e50;
  --secondary-color: #3498db;
  --bg-color: #f8f9fa;
  --text-color: #333;
  --border-color: #e0e0e0;
  --disabled-color: #95a5a6;
  --success-color: #2ecc71;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  line-height: 1.6;
  color: var(--text-color);
  background-color: var(--bg-color);
  font-size: 16px;
}

header {
  background-color: var(--primary-color);
  color: white;
  position: sticky;
  top: 0;
  z-index: 100;
  padding: 10px 15px;
}

.header-inner {
  max-width: 800px;
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

h1#header-title {
  font-size: 1.2rem;
  margin: 0;
  cursor: pointer;
}

nav .nav-btn {
  color: white;
  text-decoration: none;
  margin-left: 10px;
  font-size: 0.9rem;
}

main {
  max-width: 800px;
  margin: 0 auto;
  padding: 20px 15px;
  background-color: white;
  min-height: calc(100vh - 50px);
}

/* Home */
.part-section {
  margin-bottom: 25px;
}
.part-title {
  border-bottom: 2px solid var(--primary-color);
  padding-bottom: 5px;
  margin-bottom: 10px;
  font-size: 1.2rem;
}
.chapter-list {
  list-style: none;
}
.chapter-item {
  border-bottom: 1px solid var(--border-color);
}
.chapter-link {
  display: flex;
  justify-content: space-between;
  padding: 12px 5px;
  text-decoration: none;
  color: var(--text-color);
}
.chapter-link:hover {
  background-color: #f1f1f1;
}
.chapter-item.disabled .chapter-link {
  color: var(--disabled-color);
  pointer-events: none;
}
.chapter-status {
  font-size: 0.8rem;
}
.status-done {
  color: var(--success-color);
  font-weight: bold;
}
.status-prep {
  color: var(--disabled-color);
}

/* Chapter View */
.chapter-header {
  margin-bottom: 20px;
}
.chapter-header h1 {
  font-size: 1.5rem;
  margin-bottom: 10px;
}
.chapter-content h2 {
  font-size: 1.3rem;
  margin-top: 25px;
  margin-bottom: 10px;
  border-left: 4px solid var(--secondary-color);
  padding-left: 10px;
}
.chapter-content p {
  margin-bottom: 15px;
}
.chapter-content blockquote {
  background-color: #f4f6f7;
  border-left: 4px solid var(--primary-color);
  margin: 15px 0;
  padding: 10px;
}

/* Example Block */
.example-block {
  background-color: #f0f7fb;
  border: 1px solid #cce3f6;
  border-radius: 5px;
  padding: 15px;
  margin-bottom: 15px;
}
.example-en {
  font-size: 1.1rem;
  font-weight: bold;
  margin-bottom: 5px;
}
.example-literal, .example-translation {
  font-size: 0.9rem;
  color: #555;
}
.play-btn {
  background-color: var(--secondary-color);
  color: white;
  border: none;
  border-radius: 4px;
  padding: 5px 10px;
  margin-top: 10px;
  cursor: pointer;
  font-size: 0.9rem;
}

/* Check Section */
.check-question {
  margin-bottom: 20px;
  border: 1px solid var(--border-color);
  border-radius: 5px;
  padding: 15px;
}
.check-q {
  font-weight: bold;
  margin-bottom: 10px;
}
.check-a-container {
  display: none;
  margin-top: 10px;
  padding-top: 10px;
  border-top: 1px dashed var(--border-color);
}
.check-a-container.open {
  display: block;
}
.toggle-btn {
  background-color: #ecf0f1;
  border: 1px solid #bdc3c7;
  padding: 5px 10px;
  border-radius: 3px;
  cursor: pointer;
}
.judgment-btns {
  margin-top: 10px;
  display: flex;
  gap: 10px;
}
.btn-correct { background-color: var(--success-color); color: white; border:none; padding:5px 10px; border-radius:3px; cursor:pointer;}
.btn-wrong { background-color: #e74c3c; color: white; border:none; padding:5px 10px; border-radius:3px; cursor:pointer;}

.chapter-footer {
  margin-top: 30px;
  text-align: center;
}
.mark-read-btn {
  background-color: var(--primary-color);
  color: white;
  border: none;
  padding: 10px 20px;
  border-radius: 5px;
  font-size: 1rem;
  cursor: pointer;
}

/* Search / Index */
.search-container, .index-container {
  margin-bottom: 20px;
}
.search-input {
  width: 100%;
  padding: 10px;
  font-size: 1rem;
  border: 1px solid var(--border-color);
  border-radius: 5px;
  margin-bottom: 15px;
}
.search-result-item, .index-item {
  margin-bottom: 10px;
  padding: 10px;
  background: #f9f9f9;
  border: 1px solid #eee;
  border-radius: 4px;
}
.search-result-item a, .index-item a {
  text-decoration: none;
  color: var(--secondary-color);
  font-weight: bold;
}
.speech-controls {
  margin-bottom: 15px;
  padding: 10px;
  background: #eee;
  border-radius: 5px;
  display: flex;
  align-items: center;
  gap: 10px;
}