.bk-bookshelf {
  /* background: #111 url(img/wood.jpg); */
  margin: 0;
  /* padding: 0 0 50% 0; */
  position: relative;
  overflow: hidden;
  zoom: 1; /* Trigger "hasLayout" in IE */
}
/*
.bk-bookshelf::before {
  background: url(../image/download/shelf-left.png);
  content: '';
  display: block;
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  width: 24px;
  height: auto;
  z-index: 1;
}*/
/*
.bk-bookshelf::after {
  background: url(../image/download/shelf-right.png);
  clear: both;
  content: '';
  display: block;
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  width: 24px;
  height: auto;
  z-index: 1;
}*/

.bk-bookshelf li {
  display: block;
  float: left;
  list-style-type: none;
  padding: 0;
  position: relative;
  text-align: center;
  z-index: 2;
  margin: 10px 3.5% 40px;
  width: 18%; /* 4 horizontal items (default) */
}

/* Fallback for browsers that don't support media queries */
.bk-bookshelf li.bk-first-in-row::after {
  background: url(../image/download/shelf-2.png);
  background-repeat: no-repeat;
  content: '';
  display: block;
  position: absolute;
  right: -2048px;
  bottom: -48px;
  left: -64px;
  width: auto;
  height: 64px;
  z-index: -1;
}

.bk-bookshelf img {
  max-width: 100%;
  max-height: 100%;
}

@media (max-width: 480px) {
  .bk-bookshelf li {
    margin: 10px 1% 50px;
    width: 43%; /* 2 horizontal items (iPhone - Portrait) */
  }
  .bk-bookshelf li:nth-child(3n+1)::after {
   /* background: url(../image/download/shelf.png); 
    background-size: cover;
    content: '';
    display: block; */
    position: absolute;
    right: -2048px;
    bottom: -48px;
    left: -64px;
    width: auto;
    height: 64px;
    z-index: -1;
  }
}

@media (min-width: 480px) and (max-width: 768px) {
  .bk-bookshelf li {
    margin: 10px 4% 40px;
    width: 17%; /* 4 horizontal items (iPhone - Landscape) */
  }
  .bk-bookshelf li:nth-child(4n+1)::after {
   background: url(../image/download/shelf.png);
   background-size: cover;
    content: '';
    display: block;
    position: absolute;
    right: -2048px;
    bottom: -48px;
    left: -64px;
    width: auto;
    height: 64px;
    z-index: -1;
  }
}

@media (min-width: 768px) and (max-width: 980px) {
  .bk-bookshelf li {
    margin: 10px 3% 40px;
    width: 17%; /* 5 horizontal items (iPad - Portrait) */
  }
  .bk-bookshelf li:nth-child(5n+1)::after {
    background: url(../image/download/shelf.png);
    content: '';
    display: block;
    position: absolute;
    right: -2048px;
    bottom: -48px;
    left: -64px;
    width: auto;
    height: 64px;
    z-index: -1;
  }
}

@media (min-width: 980px) {
  .bk-bookshelf li {
    margin: 10px 3.5% 40px;
    width: 18%; /* 4 horizontal items (iPad - Landscape) */
  }
  .bk-bookshelf li:nth-child(4n+1)::after {
    background: url(../image/download/shelf-2.png);
    content: '';
    display: block;
    position: absolute;
    right: -2048px;
    bottom: -48px;
    left: -64px;
    width: auto;
    height: 64px;
    z-index: -1;
  }
}