.design:empty {
  min-width: 20px;
  min-height: 20px;
}
.design:hover {
  outline: 1px dashed red;
}
.btn-design {
  display: none;
  position: fixed;
  z-index: 99999999;
  min-width: 20px;
  min-height: 20px;
  width: 20px;
  height: 20px;
  background-color: rgba(0, 0, 0, 0.5);
  cursor: pointer;
  text-align: center;
  box-sizing: border-box !important;
  overflow: hidden;
  outline: 1px dashed red;
}
.btn-design i {
  position: absolute;
  top: calc(50% - 8px);
  left: calc(50% - 8px);
  color: #fff;
}