.wave { position: relative; }

.playhead {
  position: absolute;
  top: 0;
  bottom: 0;
  width: 2px;
  left: 0;
  background: #ff8c00;
  box-shadow: 0 0 8px rgba(255,140,0,0.9);
  pointer-events: none;
  z-index: 5;
}