.stt {
  position: fixed;
  right: 1rem;
  bottom: 1rem;
  width: 3rem;
  height: 3rem;
  border-radius: 50%;
  background: rgb(128, 128, 255) url("data:image/svg+xml;utf8,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 384 512'%3E%3Cpath fill='currentColor' d='M352 352c-8.188 0-16.38-3.125-22.62-9.375L192 205.3l-137.4 137.4c-12.5 12.5-32.75 12.5-45.25 0s-12.5-32.75 0-45.25l160-160c12.5-12.5 32.75-12.5 45.25 0l160 160c12.5 12.5 12.5 32.75 0 45.25C368.4 348.9 360.2 352 352 352z'%3E%3C/path%3E%3C/svg%3E") center no-repeat;
  box-shadow: 0 0.25rem 0.5rem 0 gray;
  opacity: 0.7;
}
.stt:hover {
  opacity: 0.8;
}
.stt:focus {
  opacity: 0.9;
}
.stt:active {
  opacity: 1;
}