button {
  height: 2.5em;
  cursor: pointer;
}

#popup {
  display: flex;
  justify-content: center;
  align-items: center;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, .7);
  z-index: 1;
}

#popup.hide {
  display: none;
}

#popup.has-filter {
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
}

#popup .content {
  padding: 3px;
  background: #fff;
  border-radius: 1px;
  box-shadow: 5px 5px 3px rgba(0, 0, 0, .3);
}

.x { position:relative; background:#000; width:30px; height:30px;float: right; }
  .x b{ position:absolute; border:solid 15px rgba(255,255,255,0); }
  
  .x b:nth-child(1){ border-top-color:#FFF; top:-2px; }
  .x b:nth-child(2){ border-left-color:#FFF; left:-2px; }
  .x b:nth-child(3){ border-bottom-color:#FFF; bottom:-2px; }
  .x b:nth-child(4){ border-right-color:#FFF; right:-2px; }