.back-fab{
  position: fixed;
  left: 16px;
  top: 16px;
  z-index: 1000;
  width: 40px;
  height: 40px;
  border-radius: 999px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: #ffffffcc;
  backdrop-filter: saturate(1.2) blur(4px);
  border: 1px solid #e4e4e4;
  color: #333;
  text-decoration: none;
  box-shadow: 0 4px 14px rgba(0,0,0,.08);
  transition: transform .1s, background .2s;
}

.back-fab:hover{
  background: #fff;
}

.back-fab:active{
  transform: scale(.97);
}

.back-fab:focus-visible{
  outline: 3px solid #66ccff;
}