fix folding cube animation

[thanapatk]

Reference Issue

As mentioned in #91, SpinKitFoldingCube's animation doesn't match

.

Fix

Using @tobiasahlin's SpinKit code,

https://github.com/tobiasahlin/SpinKit/blob/742a71277c49b69053b5beb9fad80d720840a2ab/spinkit.css#L478-L530

/*  Fold

      <div class="sk-fold">
        <div class="sk-fold-cube"></div>
        <div class="sk-fold-cube"></div>
        <div class="sk-fold-cube"></div>
        <div class="sk-fold-cube"></div>
      </div>
 */
.sk-fold {
  width: var(--sk-size);
  height: var(--sk-size);
  position: relative;
  transform: rotateZ(45deg); 
}
.sk-fold-cube {
  float: left;
  width: 50%;
  height: 50%;
  position: relative;
  transform: scale(1.1); 
}


.sk-fold-cube:before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: var(--sk-color);
  animation: sk-fold 2.4s infinite linear both;
  transform-origin: 100% 100%; 
}
.sk-fold-cube:nth-child(2) { transform: scale(1.1) rotateZ(90deg); }
.sk-fold-cube:nth-child(4) { transform: scale(1.1) rotateZ(180deg); }
.sk-fold-cube:nth-child(3) { transform: scale(1.1) rotateZ(270deg); }
.sk-fold-cube:nth-child(2):before { animation-delay: 0.3s; }
.sk-fold-cube:nth-child(4):before { animation-delay: 0.6s; }
.sk-fold-cube:nth-child(3):before { animation-delay: 0.9s; }


@keyframes sk-fold {
  0%, 10% {
    transform: perspective(140px) rotateX(-180deg);
    opacity: 0; 
  } 25%, 75% {
    transform: perspective(140px) rotateX(0deg);
    opacity: 1; 
  } 90%, 100% {
    transform: perspective(140px) rotateY(180deg);
    opacity: 0;
  } 
}

I implemented the animation according to the CSS.

[jogboms]

Thanks for fixing this @thanapatk. Sorry it took so long