/* (A) FULL SCREEN WRAPPER */
#spinner {
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  z-index: 9999;
  background: rgba(0, 0, 0, 0.5);
  transition: opacity 0.2s;
}

/* (B) CENTER LOADING SPINNER */
#spinner img {
  position: absolute;
  /*width: 70%;
  height: auto;*/
  top: 50%;
  left: 50%;
  transform: translate(-50%);
}

/* (C) SHOW & HIDE */
#spinner {
  visibility: hidden;
  opacity: 0;
}

#spinner.show {
  visibility: visible;
  opacity: 1;
}

/* (X) DOES NOT QUITE MATTER */
html,
body {
  margin: 0;
  padding: 0;
}