.loader {
   position: fixed;
   top: 0;
   left: 0;
   width: 100%;
   height: 100%;
   background-color: #ffffff;
   z-index: 100;
   transition: all 0.5s;
}
.loader img{
   position: absolute;
   top: calc(50vh - 41px);
   left: calc(50% - 41px);
   width: 82px;
   height: 82px;
   opacity: 0.6;
}
/* 読み込み完了後に「loaded」を付与する */
.loader.loaded {
   visibility: hidden;
   opacity: 0;
}