#depth-legend {
  position: absolute;
  top: 10px;
  right: 10px;
  background: rgba(255, 255, 255, 0.9);
  color: #000;
  font-size: 12px;
  padding: 8px;
  border-radius: 8px;
  box-shadow: 2px 2px 5px rgba(0,0,0,0.3);
  z-index: 20;
}
#depth-legend div {
  display: flex;
  align-items: center;
  margin-bottom: 2px;
}
#depth-legend span {
  display: inline-block;
  width: 14px;
  height: 14px;
  margin-right: 6px;
  border: 1px solid #999;
}