#svd-tts-fab{
  position: fixed;
  left: 14px;
  bottom: 14px;
  width: 50px;
  height: 50px;
  border-radius: 50%;
  background: #D32F2F; /* red */
  border: none;
  color: #fff;         /* white icon */
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 24px;     /* icon size */
  box-shadow: 0 10px 18px rgba(0,0,0,0.28);
  cursor: pointer;
  z-index: 99999;
}
#svd-tts-fab:focus { outline: none; }
#svd-tts-fab:active { transform: scale(0.98); }

@media (max-width: 600px){
  #svd-tts-fab{
    width: 46px;
    height: 46px;
    left: 12px;
    bottom: 12px;
    font-size: 22px;
  }
}