:root {
  --bg-color: #f2f4f7;
  --card-bg: #ffffff;
  --text-main: #1d1d1f;
  --text-muted: #6e6e73;
  --primary-color: #0071e3;
  --primary-hover: #005bb5;
  --accent-color: #ff9500;
  --border-color: #e5e5ea;
  --shadow: 0 4px 20px rgba(0, 0, 0, 0.06);
  --radius-lg: 18px;
  --radius-md: 12px;
  --radius-sm: 8px;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  -webkit-tap-highlight-color: transparent;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Microsoft YaHei";
  background-color: var(--bg-color);
  color: var(--text-main);
  line-height: 1.5;
  padding-bottom: 40px;
}

/* Security Auth Lock Screen */
#authOverlay {
  position: fixed;
  top: 0; left: 0; right: 0; bottom: 0;
  background: rgba(242, 244, 247, 0.96);
  backdrop-filter: blur(25px);
  -webkit-backdrop-filter: blur(25px);
  z-index: 9999;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 20px;
}

.auth-box {
  background: var(--card-bg);
  border-radius: var(--radius-lg);
  padding: 36px 28px;
  max-width: 400px;
  width: 100%;
  text-align: center;
  box-shadow: 0 12px 40px rgba(0,0,0,0.12);
  border: 1px solid var(--border-color);
}

.auth-icon {
  font-size: 48px;
  margin-bottom: 12px;
}

.auth-box h2 {
  font-size: 22px;
  font-weight: 700;
  margin-bottom: 8px;
  color: var(--text-main);
}

.auth-box p {
  font-size: 14px;
  color: var(--text-muted);
  margin-bottom: 20px;
}

.auth-input-group {
  display: flex;
  gap: 8px;
  margin-bottom: 12px;
}

.auth-input-group input {
  flex: 1;
  padding: 12px 16px;
  font-size: 16px;
  border-radius: var(--radius-md);
  border: 1px solid var(--border-color);
  outline: none;
  text-align: center;
}

.auth-input-group input:focus {
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(0, 113, 227, 0.15);
}

.auth-input-group button {
  background: var(--primary-color);
  color: white;
  border: none;
  padding: 12px 18px;
  border-radius: var(--radius-md);
  font-weight: 600;
  font-size: 15px;
  cursor: pointer;
  transition: background 0.2s;
}

.auth-input-group button:hover {
  background: var(--primary-hover);
}

.auth-error {
  display: none;
  font-size: 13px;
  color: #ff3b30;
  margin-top: 6px;
}

.lock-btn {
  background: transparent;
  border: 1px solid var(--border-color);
  padding: 6px 12px;
  border-radius: 16px;
  font-size: 13px;
  cursor: pointer;
  color: var(--text-muted);
}

.lock-btn:hover {
  background: #e5e5ea;
}

/* Glassmorphism Header */
header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border-color);
  padding: 14px 20px;
}

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

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 20px;
  font-weight: 700;
  color: var(--text-main);
}

.brand-icon {
  font-size: 24px;
}

/* Main Container */
.container {
  max-width: 800px;
  margin: 20px auto;
  padding: 0 16px;
}

/* Search and Filter Section */
.search-box {
  position: relative;
  margin-bottom: 16px;
}

.search-box input {
  width: 100%;
  padding: 14px 16px 14px 44px;
  font-size: 16px;
  border-radius: var(--radius-md);
  border: 1px solid var(--border-color);
  background: var(--card-bg);
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.03);
  outline: none;
  transition: all 0.2s ease;
}

.search-box input:focus {
  border-color: var(--primary-color);
  box-shadow: 0 0 0 4px rgba(0, 113, 227, 0.15);
}

.search-box .search-icon {
  position: absolute;
  left: 14px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-muted);
  font-size: 18px;
}

/* Filter Pills */
.series-filters {
  display: flex;
  gap: 8px;
  overflow-x: auto;
  padding-bottom: 10px;
  margin-bottom: 20px;
  scrollbar-width: none;
}

.series-filters::-webkit-scrollbar {
  display: none;
}

.pill {
  padding: 8px 16px;
  font-size: 14px;
  font-weight: 500;
  border-radius: 20px;
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  color: var(--text-muted);
  white-space: nowrap;
  cursor: pointer;
  transition: all 0.2s ease;
}

.pill.active, .pill:hover {
  background: var(--primary-color);
  color: #fff;
  border-color: var(--primary-color);
}

/* Lesson Cards Grid */
.lesson-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 16px;
}

.lesson-card {
  background: var(--card-bg);
  border-radius: var(--radius-lg);
  padding: 20px;
  border: 1px solid var(--border-color);
  box-shadow: var(--shadow);
  cursor: pointer;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
}

.lesson-card:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.1);
}

.card-badge {
  display: inline-block;
  padding: 4px 10px;
  font-size: 12px;
  font-weight: 600;
  border-radius: var(--radius-sm);
  background: #e8f2ff;
  color: var(--primary-color);
  margin-bottom: 12px;
  align-self: flex-start;
}

.card-title-zh {
  font-size: 18px;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 4px;
}

.card-title-pinyin {
  font-size: 14px;
  color: var(--text-muted);
  margin-bottom: 8px;
}

.card-title-vi {
  font-size: 14px;
  font-style: italic;
  color: var(--primary-hover);
}

/* Reader View */
.reader-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 20px;
  flex-wrap: wrap;
  gap: 12px;
}

.back-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  padding: 8px 16px;
  border-radius: 20px;
  font-size: 14px;
  font-weight: 600;
  color: var(--primary-color);
  cursor: pointer;
}

.reader-controls {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}

.control-btn {
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  padding: 8px 12px;
  border-radius: var(--radius-md);
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 6px;
}

.control-btn:hover {
  background: #f0f0f5;
}

.toggle-group {
  display: flex;
  gap: 8px;
}

.toggle-switch {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 13px;
  font-weight: 600;
  background: var(--card-bg);
  padding: 6px 10px;
  border-radius: var(--radius-md);
  border: 1px solid var(--border-color);
}

.switch {
  position: relative;
  display: inline-block;
  width: 36px;
  height: 20px;
}

.switch input {
  opacity: 0;
  width: 0;
  height: 0;
}

.slider {
  position: absolute;
  cursor: pointer;
  top: 0; left: 0; right: 0; bottom: 0;
  background-color: #ccc;
  transition: .3s;
  border-radius: 20px;
}

.slider:before {
  position: absolute;
  content: "";
  height: 14px;
  width: 14px;
  left: 3px;
  bottom: 3px;
  background-color: white;
  transition: .3s;
  border-radius: 50%;
}

input:checked + .slider {
  background-color: var(--primary-color);
}

input:checked + .slider:before {
  transform: translateX(16px);
}

/* Reader Table */
.reader-card {
  background: var(--card-bg);
  border-radius: var(--radius-lg);
  padding: 24px;
  box-shadow: var(--shadow);
  border: 1px solid var(--border-color);
}

.lesson-meta {
  margin-bottom: 24px;
  padding-bottom: 16px;
  border-bottom: 1px solid var(--border-color);
}

.lesson-meta h1 {
  font-size: 22px;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 6px;
}

.lesson-meta p {
  color: var(--text-muted);
  font-size: 15px;
}

/* 2 Column Table matching 1.1.pdf */
.bilingual-table {
  width: 100%;
  border-collapse: collapse;
}

.bilingual-table th, .bilingual-table td {
  border: 1px solid #d0d0d0;
  padding: 12px 14px;
  text-align: left;
  vertical-align: middle;
}

.bilingual-table th {
  background-color: #f8f9fa;
  font-size: 15px;
  font-weight: 700;
}

.bilingual-table tr.title-row td {
  font-weight: 700 !important;
}

.bilingual-table td.hanzi-col {
  font-size: 16px;
  font-weight: 400;
  width: 48%;
  color: #111;
}

.bilingual-table td.pinyin-col {
  font-size: 15px;
  font-weight: 400;
  width: 52%;
  color: #333;
}

.vi-subtext {
  display: block;
  font-size: 13px;
  color: #0071e3;
  font-style: italic;
  margin-top: 6px;
  font-weight: 400;
}

.audio-btn {
  display: inline-flex;
  align-items: center;
  gap: 2px;
  padding: 2px 6px;
  margin-left: 6px;
  border-radius: 10px;
  font-size: 12px;
  background: #f0f4f8;
  border: 1px solid #d0dbe5;
  cursor: pointer;
  transition: all 0.2s ease;
}

.audio-btn:hover {
  background: #e1ecf7;
  transform: scale(1.05);
}

.hide-pinyin .pinyin-col {
  visibility: hidden;
}

.hide-vi .vi-subtext {
  display: none !important;
}

@media (max-width: 600px) {
  header {
    padding: 12px 16px;
  }
  .container {
    padding: 0 12px;
  }
  .bilingual-table th, .bilingual-table td {
    padding: 10px 8px;
    font-size: 14px;
  }
  .bilingual-table td.hanzi-col {
    font-size: 15px;
  }
}