body{
  background-color: #F5F5DC;
  margin: 0;
}
ul{
  list-style-type: none;
  margin: 0;
  padding: 0;
}
.wrap{
  margin: 170px auto 0;
  width: 790px;
  height: 340px;
  position: relative;
}
.wrap ul li{
  position: absolute;
  left: 0px;
  top: 0px;
  opacity: 0;
  transition: 1s;
}
.tab{
  position: absolute;
  width: 100%;
  bottom: 15px;
  text-align: center;
}
.tab span{
  background: #fff;
  border-radius: 50%;
  width: 12px;
  height: 12px;
  display: inline-block;
}
.tab span.on{
  background: red;
}