$speed: 1s;
$l: 50px; 
$rows: 6;
$cols: 6; 
$h: $l*$rows;
$w: $l*$cols;
$cubes: $rows*$cols; 
//$timing: cubic-bezier(1,0.49,0.69,1);
$timing: linear;
$delay: $speed/$cubes;
//$delay: 0; 

body {
  background: #306989;
}
.wall {
  position: relative;
  perspective: 700px;
  height: $h;
  width: $w;
  margin: 5vh auto;
  display: flex;
  flex-flow: wrap;
  visibility: hidden;
  &, * {
    backface-visibility: hidden;
    transform-style: preserve-3d;
  }
  .overlay {
    visibility: visible;
    position: absolute;
    display: block;
    top: 0;
    left: 0;
    width: $w;
    height: $h;
    transform: translatez($l/2);
    background-size: $w $h;
    transition: opacity 0.1s;
  }
}

.nav {
  position: absolute;
  top: 50%;
  left: $l*(-2/sqrt(2));
  right: $l*(-2/sqrt(2));
  height: 2px;
  
  .button {
    position: absolute;
    z-index: 99;
    top: 50%;
    height: $l;
    width: $l;
    margin-top: $l/-2;
    color: #888;
    font-family: monospace;
    text-align: center;
    cursor: pointer;
    visibility: visible;
    svg {
      position: relative;
      width: auto;
      margin: auto;
      height: 100%;
    }
    path {
      fill: currentcolor;
    }
    &:hover {
      color: #000;
    }
    
    &.prev {
      left: 0;
    }
    &.next {
      right: 0;
    }
  }
  
  
}

.cube {
  flex: 0 0 $l;
  height: $l;
  position: relative;
  pointer-events: none;
  animation-duration: $speed;
  animation-timing-function: $timing;
  animation-fill-mode: forwards;
  &.sliding {

    animation-play-state: running; 
    
    &.up {
      animation-name: switch-up;
    }
    &.down {
      animation-name: switch-down;
    }
    &.left {
      animation-name: switch-left;
    }
    &.right {
      animation-name: switch-right;
    }    
    @at-root {
      @keyframes switch-up {
        0% , 10%{
          transform: 
            scale(1) 
            rotatex(0);
        }
        40% {
          transform: 
            scale(1/sqrt(2))
            translatez($l)
            rotatex(0);
        }
        70% {
          transform: 
            scale(1/sqrt(2))
            translatez($l)
            rotatex(90deg);
        }
        100% {
          transform: 
            scale(1) 
            rotatex(90deg);
        }
      }
    }
    @at-root {
      @keyframes switch-right {
        0% , 10%{
          transform: 
            scale(1) 
            rotatey(0);
        }
        40% {
          transform: 
            scale(1/sqrt(2))
            translatez($l)
            rotatey(0);
        }
        70% {
          transform: 
            scale(1/sqrt(2))
            translatez($l)
            rotatey(-90deg);
        }
        100% {
          transform: 
            scale(1) 
            rotatey(-90deg);
        }
      }
    }
    @at-root {
      @keyframes switch-left {
        0% , 10%{
          transform: 
            scale(1) 
            rotatey(0);
        }
        40% {
          transform: 
            scale(1/sqrt(2))
            translatez($l)
            rotatey(0);
        }
        70% {
          transform: 
            scale(1/sqrt(2))
            translatez($l)
            rotatey(90deg);
        }
        100% {
          transform: 
            scale(1) 
            rotatey(90deg);
        }
      }
    }
    @at-root {
      @keyframes switch-down {
        0% , 10%{
          transform: 
            scale(1) 
            rotatex(0);
        }
        40% {
          transform: 
            scale(1/sqrt(2)) 
            translatez($l)
            rotatex(0);
        }
        70% {
          transform: 
            scale(1/sqrt(2)) 
            translatez($l)
           rotatex(-90deg);
        }
        100% {
          transform: 
            scale(1) 
            rotatex(-90deg);
        }
      }
    }
  }
  @for $i from 1 through $cubes {
    &:nth-child(#{$i}) {
      animation-delay: $delay*$i; 
      .side {
        background-position: 
          ($l*-1*($i%$cols) + $l) 
          ($l*-1*ceil($i/$cols) + $l);   
      }
    }
  }
  .side {
    visibility: visible;
    position: absolute;
    top: 0;
    left: 0;
    width: $l;
    height: $l;
    background-size: $w $h;
    background-color: #000;
    
    @for $i from 0 to 6 {
    &:nth-child(#{$i + 1}) {

      transform: if($i == 2 , rotate(180deg), rotate(0deg)) if($i < 4, rotateY($i*90deg) , rotateX(pow(-1, $i)*90deg)) translateZ($l/2);
    }
  }
  }
}