<div class="slider">
  <!-- slides -->
  <div class="slider__slides">
    <div class="slide s--active">
      <div class="slide__inner">
        <div class="slide__content">
          <h2 class="slide__heading">Clip-Path Revealing Slider</h2>
          <p class="slide__text">Greetings, Traveler!</p>
        </div>
      </div>
    </div>
    <div class="slide">
      <div class="slide__inner">
        <div class="slide__content">
          <h2 class="slide__heading">Simple Animation</h2>
          <p class="slide__text">Clip-path magic!</p>
        </div>
      </div>
    </div>
    <div class="slide">
      <div class="slide__inner">
        <div class="slide__content">
          <h2 class="slide__heading">Very Stylish Effect!</h2>
          <p class="slide__text">It looks cool, isn't it?</p>
        </div>
      </div>
    </div>
    <div class="slide">
      <div class="slide__inner">
        <div class="slide__content">
          <h2 class="slide__heading">Limited browser support</h2>
          <p class="slide__text">Forget about IE/Edge and FF</p>
        </div>
      </div>
    </div>
    <div class="slide s--prev">
      <div class="slide__inner">
        <div class="slide__content">
          <h2 class="slide__heading">Check my other stuff!</h2>
          <p class="slide__text"><a href="https://codepen.io/suez/pens/public/" target="_blank">Other demos</a> and <a href="https://twitter.com/NikolayTalanov" target="_blank">Twitter</a></p>
        </div>
      </div>
    </div>
  </div>
  <!-- slides end -->
  <div class="slider__control">
    <div class="slider__control-line"></div>
    <div class="slider__control-line"></div>
  </div>
  <div class="slider__control slider__control--right m--right">
    <div class="slider__control-line"></div>
    <div class="slider__control-line"></div>
  </div>
</div>

*, *:before, *:after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  overflow: hidden;
  font-family: Helvetica, Arial, sans-serif;
}

$numOfSlides: 5;
$slidingAT: 1.3s;
$controlSize: 60px;

.slider {
  position: relative;
  height: 100vh;

  &__slides {
    z-index: 1;
    position: relative;
    height: 100%;
  }

  &__control {
    z-index: 2;
    position: absolute;
    top: 50%;
    left: 5%;
    width: $controlSize;
    height: $controlSize;
    margin-left: $controlSize/-2;
    margin-top: $controlSize/-2;
    border-radius: 50%;
    background: #fff;
    transition: background-color 0.3s;
    cursor: pointer;

    &--right {
      left: 95%;
    }
    
    &:hover {
      background-color: #2da6ff;
    }

    &-line {
      position: absolute;
      left: 23px;
      top: 50%;
      width: 3px;
      height: 14px;
      transform-origin: 50% 0;
      transform: rotate(-45deg);

      &:nth-child(2) {
        transform: translateY(1px) rotate(-135deg);
      }

      .slider__control--right & {
        left: 37px;
        transform-origin: 1px 0;
        transform: rotate(45deg);

        &:nth-child(2) {
          transform: translateY(1px) rotate(135deg);
        }
      }

      &:after {
        content: "";
        position: absolute;
        left: 0;
        top: 0;
        width: 100%;
        height: 100%;
        background-color: #e2e2e2;
        transition: background-color 0.3s;
      }

      .slider__control:hover &:after {
        background-color: #fff;
      }

      .slider__control.a--rotation & {

        &:after {
          animation: arrowLineRotation 0.49s;
        }

        &:nth-child(1):after {
          animation: arrowLineRotationRev 0.49s;
        }
      }
    }
  }
}

@keyframes arrowLineRotation {
  to {
    transform: rotate(180deg);
  }
}

@keyframes arrowLineRotationRev {
  to {
    transform: rotate(-180deg);
  }
}

.slide {
  overflow: hidden;
  position: absolute;
  left: 50%;
  top: 50%;
  width: 150vmax;
  height: 150vmax;
  transform: translate(-50%, -50%);
  border-radius: 50%;
  transition: clip-path 0s $slidingAT*0.7;
  clip-path: circle($controlSize/2 at 120vw 50%);

  &.s--prev {
    clip-path: circle($controlSize/2 at 30vw 50%);
  }

  &.s--active {
    z-index: 1;
    transition: clip-path $slidingAT;
    clip-path: circle(120vmax at 120vw 50%);
    
    &.s--active-prev {
      clip-path: circle(120vmax at 30vw 50%);
    }
  }

  @for $i from 1 through $numOfSlides {
    &:nth-child(#{$i}) {
      .slide__inner {
        background-image: url('https://s3-us-west-2.amazonaws.com/s.cdpn.io/142996/onepgscr-#{$i+1}.jpg');
      }
    }
  }

  &__inner {
    position: absolute;
    left: 50%;
    top: 50%;
    width: 100vw;
    height: 100vh;
    margin-left: -50vw;
    margin-top: -50vh;
    background-size: cover;
    background-position: center center;

    &:before {
      content: "";
      position: absolute;
      left: 0;
      top: 0;
      width: 100%;
      height: 100%;
      background: rgba(0,0,0,0.3);
    }
  }

  &__content {
    position: absolute;
    left: 5%;
    top: 50%;
    margin-left: $controlSize/-2;
    margin-top: $controlSize*0.8;
    max-width: 480px;
    color: #fff;
  }

  &__heading {
    margin-bottom: 20px;
    font-size: 60px;
  }

  &__text {
    font-size: 25px;

    a {
      color: inherit;
    }
  }
}

(function() {
  var $slides = document.querySelectorAll('.slide');
  var $controls = document.querySelectorAll('.slider__control');
  var numOfSlides = $slides.length;
  var slidingAT = 1300; // sync this with scss variable
  var slidingBlocked = false;

  [].slice.call($slides).forEach(function($el, index) {
    var i = index + 1;
    $el.classList.add('slide-' + i);
    $el.dataset.slide = i;
  });

  [].slice.call($controls).forEach(function($el) {
    $el.addEventListener('click', controlClickHandler);
  });

  function controlClickHandler() {
    if (slidingBlocked) return;
    slidingBlocked = true;

    var $control = this;
    var isRight = $control.classList.contains('m--right');
    var $curActive = document.querySelector('.slide.s--active');
    var index = +$curActive.dataset.slide;
    (isRight) ? index++ : index--;
    if (index < 1) index = numOfSlides;
    if (index > numOfSlides) index = 1;
    var $newActive = document.querySelector('.slide-' + index);

    $control.classList.add('a--rotation');
    $curActive.classList.remove('s--active', 's--active-prev');
    document.querySelector('.slide.s--prev').classList.remove('s--prev');
    
    $newActive.classList.add('s--active');
    if (!isRight) $newActive.classList.add('s--active-prev');
    

    var prevIndex = index - 1;
    if (prevIndex < 1) prevIndex = numOfSlides;

    document.querySelector('.slide-' + prevIndex).classList.add('s--prev');

    setTimeout(function() {
      $control.classList.remove('a--rotation');
      slidingBlocked = false;
    }, slidingAT*0.75);
  };
}());