:root {
  --bg: #0b0f1a;
  --bg2: #121829;
  --fg: #e8ecf4;
  --muted: #8892a8;
  --accent: #4f8cff;
  --accent2: #7a5cff;
  --danger: #ff4f6b;
  --border: #273049;
  --radius: 14px;
}
* { box-sizing: border-box; }
html, body {
  margin: 0; padding: 0;
  background: radial-gradient(1200px 600px at 20% -10%, #1b2446 0%, var(--bg) 50%) fixed;
  color: var(--fg);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang TC",
               "Microsoft JhengHei", "Noto Sans TC", Roboto, sans-serif;
  min-height: 100vh;
}
header {
  text-align: center;
  padding: 28px 16px 8px;
}
header h1 {
  margin: 0;
  font-size: 28px;
  letter-spacing: 2px;
  background: linear-gradient(90deg, var(--accent), var(--accent2));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.subtitle { color: var(--muted); margin: 6px 0 0; font-size: 14px; }
footer { text-align: center; color: var(--muted); padding: 24px 12px 32px; }

.panel {
  max-width: 720px;
  margin: 16px auto;
  padding: 20px;
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: 0 10px 40px rgba(0,0,0,0.35);
}
.hidden { display: none !important; }

h2 { margin: 0 0 14px; font-size: 20px; }

/* 模式選擇 */
.mode-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-bottom: 16px;
}
@media (max-width: 520px) { .mode-grid { grid-template-columns: 1fr; } }
.mode-card {
  background: linear-gradient(160deg, #1a2342, #141a30);
  border: 1px solid var(--border);
  color: var(--fg);
  padding: 22px 16px;
  border-radius: var(--radius);
  text-align: left;
  cursor: pointer;
  transition: transform .15s, border-color .15s;
}
.mode-card:hover { transform: translateY(-2px); border-color: var(--accent); }
.mode-card .icon { font-size: 32px; }
.mode-card .title { font-size: 18px; font-weight: 600; margin-top: 8px; }
.mode-card .desc { color: var(--muted); font-size: 13px; margin-top: 4px; }

/* 房間碼輸入 */
.room-box label {
  display: block;
  font-size: 13px;
  color: var(--muted);
  margin-bottom: 6px;
}
.room-input-row { display: flex; gap: 8px; }
.room-input-row input {
  flex: 1;
  background: #0c1224;
  border: 1px solid var(--border);
  border-radius: 10px;
  color: var(--fg);
  padding: 12px 14px;
  font-size: 18px;
  letter-spacing: 4px;
  text-transform: uppercase;
  text-align: center;
}
.room-input-row input:focus {
  outline: none;
  border-color: var(--accent);
}
.hint { color: var(--muted); font-size: 12px; margin: 8px 0 0; }

/* 按鈕 */
button {
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: 10px;
  padding: 11px 16px;
  font-size: 15px;
  cursor: pointer;
  transition: background .15s, transform .1s;
}
button:hover { background: #5d96ff; }
button:active { transform: scale(0.98); }
button.ghost {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--fg);
}
button.danger { background: var(--danger); }
button.danger:hover { background: #ff6680; }

.source-row {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 12px;
}

.status {
  background: #0c1224;
  border: 1px dashed var(--border);
  color: var(--muted);
  padding: 10px 12px;
  border-radius: 10px;
  font-size: 13px;
  margin-bottom: 12px;
}
.status.ok { color: #63e6a5; border-color: #2a5d46; }
.status.err { color: #ff8fa2; border-color: #5d2a38; }

/* Video */
.preview-wrap {
  background: #000;
  border-radius: var(--radius);
  overflow: hidden;
  aspect-ratio: 16 / 9;
  margin-bottom: 12px;
}
.preview-wrap.full { aspect-ratio: auto; min-height: 50vh; }
video {
  width: 100%;
  height: 100%;
  display: block;
  object-fit: contain;
  background: #000;
}

/* QR */
.qr-area {
  text-align: center;
  padding: 14px;
  background: #0c1224;
  border-radius: 10px;
  margin-bottom: 12px;
}
.qr-area strong {
  color: var(--accent);
  letter-spacing: 4px;
  font-size: 22px;
}
#qrcode { display: inline-block; padding: 10px; background: #fff; border-radius: 8px; margin-top: 8px; }
#qrcode canvas, #qrcode img { display: block; }

/* 接收端控制 */
.recv-controls { display: flex; gap: 8px; flex-wrap: wrap; }
.recv-controls button { flex: 1; min-width: 110px; }