.cover-slider__wrap {
    background-image: url("../images/slide/slide_frame.png");

    background-size:cover;
    background-position:center;
    position: relative;
    max-width: 450px;
    height: 672px;
    margin: 2em auto;
    padding: 5em 1em;
    color: #fff;
    line-height: 2;
    font-family: 'Trebuchet MS', sans-serif;
    font-weight: bold;
    
}
.cover-slider__inner {
    position: relative;
    min-height: 40em;
    text-align: center;
    z-index: 10;
}
.cover-slider {
    backface-visibility: hidden;
}
.cover-slider__slide {
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 100%;
    padding: 0;
    margin: 0;
    background-size: cover;
    background-position: center;
    list-style: none;
    z-index: 0;
    opacity: .5;
    &.active {
        animation-duration: 2500ms;
        animation-name: slidein;
        animation-fill-mode: forwards;
    }
    &.inactive {
        animation-duration: 2500ms;
        animation-name: slideout;
        animation-fill-mode: forwards;
    }
    @keyframes slidein {
        from {
            left: 0;
            right: 100%;
        }
        to {
            left: 0;
            right: 0;
        }
    }
    @keyframes slideout {
        from {
            left: 0;
            right: 0;
        }
        to {
            left: 100%;
            right: 0;
        }
    }
}
.cover-slider__slide {
    &:nth-child(1){
        background-image: url("https://unsplash.it/640/480") !important;
    }
    &:nth-child(2){
        background-image: url("https://unsplash.it/641/480");
    }
    &:nth-child(3){
        background-image: url("https://unsplash.it/641/481");
    }
    &:nth-child(4){
        background-image: url("https://unsplash.it/643/482");
    }
}
body {
    background: teal;
    box-sizing: border-box;
}
*, *:before, *:after {
    box-sizing: inherit;
}
.hide {
    position: absolute;
    left: -9999px;
}





#slider {
  position: absolute;
  overflow: hidden;
  margin: 20px auto 0 auto;
  border-radius: 4px;
  top:21px;
  right: 18px;
}

#slider ul {
  position: relative;
  margin: 0;
  padding: 0;
  height: 200px;
  list-style: none;
}

#slider ul li {
  position: relative;
  display: block;
  float: left;
  margin: 0;
  padding: 0;
  width: 411px;
  height: 411px;
  background: #ccc;
  text-align: center;
  line-height: 300px;
}

a.control_prev, a.control_next {
  position: absolute;
  top: 40%;
  z-index: 999;
  display: block;
  padding: 4% 3%;
  width: auto;
  height: auto;
  background: #2a2a2a;
  color: #fff;
  text-decoration: none;
  font-weight: 600;
  font-size: 18px;
  opacity: 0.8;
  cursor: pointer;
}

a.control_prev:hover, a.control_next:hover {
  opacity: 1;
  -webkit-transition: all 0.2s ease;
}

a.control_prev {
  border-radius: 0 2px 2px 0;
}

a.control_next {
  right: 0;
  border-radius: 2px 0 0 2px;
}

.slider_option {
  position: relative;
  margin: 10px auto;
  width: 160px;
  font-size: 18px;
}