.prebox {
  /* height: 100%; */
  top: 100px;
  bottom: 56px;
  background: rgb(0, 0, 0, 0.6);
  position: absolute;
  /* top: 0; */
  right: 0;
  z-index: 999;
  box-sizing: border-box;
  color: #fff;
}

.prebox ul {
  height: 100%;
  overflow-y: auto;
  display: flex;
  flex-wrap: wrap;
  flex-direction: row;
}

.prebox ul li {
  /*float: left;*/
  text-align: center;
  margin-bottom: 20px;
  font-size: 14px;
  line-height: 30px;
}

.prebox li img {
  width: 80%;
}

.pre-btn {
  display: block;
  position: absolute;
  box-sizing: border-box;
  padding-left: 15px;
  width: 55px;
  height: 30px;
  left: -55px;
  top: 2%;
  font-size: 16px;
  line-height: 30px;
  cursor: pointer;
  box-shadow: -2px 4px 2px rgb(0, 0, 0, 0.2);
  opacity: 0.7;
}

.pre-btn:hover {
  text-decoration-line: none;
  opacity: 1;
}

.prebtn01 {
  background: url('/ebook/arrow-left.png') no-repeat 2px center #b61b22;
}

.prebtn02 {
  display: none;
  background: url('/ebook/arrow-right.png') no-repeat 2px center #b61b22;
}

@media screen and (max-width: 999px) {
  .prebox {
    width: 80%;
    padding: 30px 10px;
  }

  .prebox ul li {
    width: 50%;
  }
}

@media screen and (min-width: 1000px) {
  .prebox {
    width: 25%;
    padding: 50px 40px;
  }

  .prebox ul li {
    width: 33.3%;
  }
}