<div class="rwd_slider_container_wrapper">
  <div class="rwd_slider_container">
    <div class="slider_container" >
      <div>
        <img src="https://via.placeholder.com/400x280.png?text=1" alt="pure css slider" width="400" height="280" />
      </div>
      <div>
        <img src="https://via.placeholder.com/400x280.png?text=2" alt="pure css slider" width="400" height="280" />
      </div>
      <div>
        <img src="https://via.placeholder.com/400x280.png?text=3" alt="pure css slider" width="400" height="280" />
      </div>
      <div>
        <img src="https://via.placeholder.com/400x280.png?text=4" alt="pure css slider" width="400" height="280" />
      </div>
      <div>
        <img src="https://via.placeholder.com/400x280.png?text=5" alt="pure css slider" width="400" height="280" />
      </div>
    </div><!-- end of .pure_slider_container -->
  </div><!-- end of .embed-responsive -->
</div><!-- end of .embed-responsive-box -->

.slider_container {
  margin: 30px auto;
  width: 400px;
  height: 280px;
  overflow: hidden;
  position: relative;
  border: 10px solid;
  border-top-color: #856036;
  border-left-color: #5d4426;
  border-bottom-color: #856036;
  border-right-color: #5d4426;
  background-color: #f5f5f5;
}
.slider_container:before {
  content: '';
  display: block;
  position: absolute;
  top: 0;
  left: -100%;
  opacity: 1;
  filter: alpha(opacity=100);
  width: 100%;
  height: 100%;
  background-image: url(http://blog.shihshih.com/wp-content/uploads/2018/08/image1.png);
  animation: bk 25s linear;
}
.slider_container div {
  position: absolute;
  top: 0;
  left: 0;
  opacity: 1;
  filter: alpha(opacity=100);
  left: 100%;
  width: 100%;
  -webkit-animation: round 25s linear infinite;
  animation: round 25s linear infinite;
}
.slider_container div img {
  width: 100%;
}
@-webkit-keyframes round {
  4% {
    opacity: 1;
    filter: alpha(opacity=100);
    left: 0;
    /* 0 - 1秒 滑入*/
  }
  20% {
    opacity: 1;
    filter: alpha(opacity=100);
    left: 0;
    /* 1- 5秒靜止*/
  }
  24% {
    opacity: 1;
    filter: alpha(opacity=100);
    left: -100%;
    /* 5-6秒滑出*/
  }
  26% {
    opacity: 0;
    filter: alpha(opacity=0);
    left: -100%;
    /* 6-6.5秒變透明*/
  } 
  28% {
    opacity: 0;
    filter: alpha(opacity=0);
    left: 100%;
    /* 6.5-7秒回到起始位置*/
  } 
}
@keyframes bk {
  0% {
    left: 0;
    /* 初始位置*/
  }
  4% {
    left: -100%;
    /* 0 - 1秒 滑出*/
  }   
}

@keyframes bk {
  0% {
    left: 0;
    /* 初始位置*/
  }
  4% {
    left: -100%;
    /* 0 - 1秒 滑出*/
  }  
}
.slider_container div:nth-child(5) {
  -webkit-animation-delay: 0s;
  animation-delay: 0s;
}
.slider_container div:nth-child(4) {
  -webkit-animation-delay: 5s;
  animation-delay: 5s;
}
.slider_container div:nth-child(3) {
  -webkit-animation-delay: 10s;
  animation-delay: 10s;
}
.slider_container div:nth-child(2) {
  -webkit-animation-delay: 15s;
  animation-delay: 15s;
}
.slider_container div:nth-child(1) {
  -webkit-animation-delay: 20s;
  animation-delay: 20s;
}
.rwd_slider_container_wrapper {
  margin: 30px auto !important;
  width: 420px;
}
.rwd_slider_container {
  position: relative;
  display: block;
  height: 0;
  padding: 0;
  overflow: hidden;
  padding-bottom: 70%;
  box-sizing: border-box;
}
.rwd_slider_container .slider_container {
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  width: 100%;
  height: 100%;
  margin: 0;
  box-sizing: border-box;
}