:root {
  /* 替換為展示企業藍 */
  --primary-color: #1e3a8a;
  --primary-hover: #1e40af;
  --bg-color: #f3f4f6;
  --card-bg: #ffffff;
  --text-main: #1f2937;
  --text-muted: #6b7280;
  --border-color: #e5e7eb;
  --danger-color: #dc2626;
  --success-color: #059669;
  --focus-ring: #2563eb;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Microsoft JhengHei", sans-serif;
  background-color: var(--bg-color);
  color: var(--text-main);
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 20px;
}

/* 鍵盤操作無障礙 Focus 樣式 */
button:focus-visible,
input:focus-visible,
select:focus-visible {
  outline: 3px solid var(--focus-ring);
  outline-offset: 2px;
}

/* 主卡片容器 */
.card {
  background: var(--card-bg);
  border-radius: 12px;
  box-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.1), 0 8px 10px -6px rgba(0, 0, 0, 0.05);
  width: 100%;
  max-width: 980px;
  overflow: hidden;
  display: flex;
  flex-direction: column;
}

/* 頂部標題與雙語開關 */
header {
  background-color: var(--primary-color);
  color: #ffffff;
  padding: 16px 24px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

header h1 {
  font-size: 20px;
  font-weight: 700;
  display: inline-block;
  margin-right: 12px;
}

.badge {
  background: rgba(255, 255, 255, 0.2);
  padding: 3px 8px;
  border-radius: 20px;
  font-size: 12px;
  vertical-align: middle;
}

.lang-switch {
  display: flex;
  gap: 4px;
  background: rgba(0, 0, 0, 0.25);
  padding: 3px;
  border-radius: 6px;
}

.btn-lang {
  background: transparent;
  border: none;
  color: #ffffff;
  padding: 4px 10px;
  font-size: 12px;
  font-weight: 600;
  border-radius: 4px;
  cursor: pointer;
  transition: background 0.2s;
}

.btn-lang.active {
  background: #ffffff;
  color: var(--primary-color);
}

/* 左右分欄 Grid */
.grid {
  display: grid;
  grid-template-columns: 360px 1fr;
  min-height: 520px;
}

/* 左側控制面板 */
.controls {
  padding: 24px;
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.form-group label {
  font-size: 13px;
  font-weight: 600;
  color: #374151;
}

.form-group input,
.form-group select {
  padding: 9px 12px;
  border: 1px solid #d1d5db;
  border-radius: 6px;
  font-size: 14px;
  transition: border-color 0.2s;
  background: #fff;
}

/* 針對 HTML5 原生 time 選擇器美化 */
.form-group input[type="time"] {
  font-family: inherit;
  color: #1f2937;
  cursor: pointer;
}

.form-group input:focus,
.form-group select:focus {
  border-color: var(--primary-color);
  outline: none;
}

.email-box {
  display: flex;
  align-items: center;
  border: 1px solid #d1d5db;
  border-radius: 6px;
  overflow: hidden;
}

.email-box input {
  border: none;
  border-radius: 0;
  flex: 1;
}

.email-box span {
  background: #f9fafb;
  padding: 9px 8px;
  font-size: 13px;
  color: var(--text-muted);
  border-left: 1px solid #d1d5db;
  white-space: nowrap;
}

.btn-primary {
  background-color: var(--primary-color);
  color: #ffffff;
  border: none;
  border-radius: 6px;
  padding: 12px;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.2s;
  margin-top: 6px;
}

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

/* 右側展示面板 */
.display-box {
  padding: 24px;
  display: flex;
  justify-content: center;
  align-items: center;
  background: #fafafa;
  text-align: center;
}

#activeView {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  width: 100%;
}

.session-tag {
  background: #dbeafe; /* 替換為展示藍 */
  color: var(--primary-color);
  padding: 4px 10px;
  border-radius: 4px;
  font-weight: 700;
  font-size: 12px;
  letter-spacing: 0.5px;
  display: inline-block;
  margin-bottom: 8px;
}

/* 課堂地點與時段備註 */
#lblSubMeta {
  font-size: 13px;
  color: #4b5563;
  margin-bottom: 8px;
  line-height: 1.4;
}

/* 核心 QR Code 容器：抵抗投影機反光 */
#qrcode-box {
  background: #ffffff;
  padding: 16px;
  border-radius: 12px;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
  margin: 8px auto;
  display: inline-flex;
  justify-content: center;
  align-items: center;
}

#qrcode-box canvas,
#qrcode-box img {
  display: block;
  image-rendering: pixelated;
  width: 220px;
  height: 220px;
}

/* 現場操作按鈕列 */
.action-links {
  display: flex;
  gap: 10px;
  margin-top: 14px;
  flex-wrap: wrap;
  justify-content: center;
}

.action-links button {
  background: #ffffff;
  border: 1px solid #d1d5db;
  border-radius: 6px;
  padding: 8px 14px;
  font-size: 13px;
  font-weight: 500;
  cursor: pointer;
  color: #374151;
  transition: all 0.2s;
}

.action-links button:hover {
  background: #f3f4f6;
  border-color: #9ca3af;
}

/* 立即發信按鈕：微反白高亮提升辨識度 */
#i18n-btn-early-end {
  border-color: #93c5fd;
  color: #1d4ed8;
  background-color: #eff6ff;
}

#i18n-btn-early-end:hover {
  background-color: #dbeafe;
  border-color: #60a5fa;
}

/* =========================================================
   全螢幕投影模式 (Fullscreen Presentation Mode)
   ========================================================= */
:fullscreen,
::backdrop {
  background-color: #0f172a !important;
}

:fullscreen .card {
  max-width: 100vw;
  width: 100vw;
  height: 100vh;
  border-radius: 0;
  box-shadow: none;
  background: #ffffff;
  display: flex;
}

:fullscreen header,
:fullscreen .controls {
  display: none !important;
}

:fullscreen .grid {
  display: flex;
  flex: 1;
  width: 100vw;
  height: 100vh;
}

:fullscreen .display-box {
  flex: 1;
  width: 100%;
  height: 100%;
  background: #ffffff;
  padding: 2vh 4vw;
}

:fullscreen #lblTitle {
  font-size: 3.5vmin !important;
  font-weight: 800;
  color: #0f172a;
  margin-bottom: 0.5vmin;
}

:fullscreen #lblSubMeta {
  font-size: 1.8vmin !important;
  margin-bottom: 1.5vmin;
}

:fullscreen .session-tag {
  font-size: 1.8vmin !important;
  padding: 6px 14px;
}

/* 全螢幕下 QR Code 極大化並保持清晰 */
:fullscreen #qrcode-box {
  padding: 2.2vmin;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.15);
  margin: 1vmin auto;
}

:fullscreen #qrcode-box canvas,
:fullscreen #qrcode-box img {
  width: 48vmin !important;
  height: 48vmin !important;
}

:fullscreen #i18n-scan-hint {
  font-size: 2.3vmin !important;
  font-weight: 700;
  color: #1e293b;
}

:fullscreen .privacy-text {
  font-size: 1.2vmin !important;
  max-width: 70vw;
  color: #94a3b8;
  border: none;
  margin-top: 1vmin;
}

:fullscreen .paper-backup-alert {
  font-size: 1.3vmin !important;
  margin-top: 4px;
}

/* 全螢幕懸浮操作欄 */
:fullscreen .action-links {
  position: fixed;
  bottom: 20px;
  left: 50%;
  transform: translateX(-50%);
  background: rgba(255, 255, 255, 0.96);
  padding: 8px 18px;
  border-radius: 30px;
  box-shadow: 0 6px 20px rgba(0, 0, 0, 0.2);
  opacity: 0.15;
  transition: opacity 0.3s ease;
  z-index: 100;
}

:fullscreen .action-links:hover {
  opacity: 1;
}

/* =========================================================
   Modal 樣式 (Plan B)
   ========================================================= */
.modal {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.65);
  backdrop-filter: blur(3px);
  display: none;
  justify-content: center;
  align-items: center;
  z-index: 9999; /* 保證無論是否全螢幕都能覆蓋在最上層 */
  padding: 16px;
}

.modal-content {
  background: #ffffff;
  border-radius: 10px;
  padding: 24px;
  width: 100%;
  max-width: 440px;
  box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.25);
  text-align: left;
}

/* 手機與平板響應式適配 */
@media (max-width: 768px) {
  .grid {
    grid-template-columns: 1fr;
  }
  .controls {
    border-right: none;
    border-bottom: 1px solid var(--border-color);
  }
  #qrcode-box canvas,
  #qrcode-box img {
    width: 180px;
    height: 180px;
  }
}