Exploring the concept of "folding" elements through the use of rotate3d(), I encountered an issue with only one side of my fold. During the animation, the z-index seems to be ignored, but suddenly jumps to the top at the end. My suspicion lies in the z-axis component of rotate3d() (similar to this scenario), yet the puzzling part is why it only affects one of the two elements.
var button = $('.button');
var open = true;
button.click(() => {
var right = $('.triangle.topright');
var left = $('.triangle.topleft');
if (open) {
right.addClass('r-close');
left.addClass('l-close');
} else {
right.removeClass('r-close');
left.removeClass('l-close');
}
open = !open;
});.container {
box-sizing: border-box;
display: flex;
padding: 50px 75px;
position: relative;
height: 300px;
width: 100%;
}
.fold.r-close {
transform-origin: left;
transform: rotate3d(0, 1, 0, 90deg);
}
.fold {
box-sizing: border-box;
display: inline-block;
height: 100px;
width: 100px;
position: relative;
transition: all 1.5s;
transform-style: preserve-3d;
}
.fold.outer {
width: 150px;
}
.fold.left {
margin-left: 50px;
}
.triangle {
height: 0;
position: absolute;
transition: all 1.5s;
width: 0;
}
/* middle */
.triangle.middle {
top: 0;
z-index: -1 !important;
}
.triangle.middle.left {
border-bottom: 100px solid pink;
border-left: 100px solid transparent;
right: 0;
}
.triangle.middle.right {
border-bottom: 100px solid pink;
border-right: 100px solid transparent;
left: 0;
}
/* right fold */
.triangle.topright.front {
border-bottom: 100px solid red;
border-right: 100px solid transparent;
backface-visibility: hidden;
transform: rotate3d(1, 1, 0, 180deg);
}
.triangle.topright.back {
backface-visibility: hidden;
border-left: 100px solid transparent;
border-top: 100px solid pink;
left: -0.6px;
}
/* left fold */
.triangle.topleft.front {
border-bottom: 100px solid red;
border-left: 100px solid transparent;
backface-visibility: hidden;
transform: rotate3d(-1, 1, 0, 180deg);
}
.triangle.topleft.back {
backface-visibility: hidden;
border-top: 100px solid pink;
border-right: 100px solid transparent;
right: -0.6px;
}
/* folds */
.r-close.back {
transform: rotate3d(1, 1, 0, 180deg);
}
.triangle.r-close.front {
transform: rotate3d(1, 1, 0, 0deg);
}
.l-close.back {
transform: rotate3d(-1, 1, 0, 180deg);
}
.triangle.l-close.front {
transform: rotate3d(-1, 1, 0, 0deg);
}
.button {
bottom: 0;
position: absolute;
}<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="container">
<div class="fold outer">
<div class="triangle middle left"></div>
<div class="fold left">
<div class="triangle topleft front"></div>
<div class="triangle topleft back"></div>
</div>
</div>
<div class="fold outer">
<div class="triangle middle right"></div>
<div class="fold right">
<div class="triangle topright front"></div>
<div class="triangle topright back"></div>
</div>
</div>
<button class="button">Click</button>
</div>