CSS を使用してグラフィック変形ポップアップ効果を作成する

<section class="cd-section">
<!-- section content here -->
<p class="cd-modal-action">
<a href="#0" class="btn" data-type="modal-trigger">Fire Modal Window</a> <!— 这是窗体按钮 -->
<span class="cd-modal-bg"></span>
</p>
<p class="cd-modal">
<p class="cd-modal-content">
<!— 这是窗体内容区域 -->
</p>
</p>
<a href="#0" class="cd-modal-close">Close</a> <!— 这是关闭按钮 -->
</section>

.cd-modal-action {   
position: relative;   
}   
.cd-modal-action .btn {   
width: 12.5em;   
height: 4em;   
background-color: #123758;   
border-radius: 5em;   
transition: color 0.2s 0.3s, width 0.3s 0s;   
}   
.cd-modal-action .btn.to-circle {   
width: 4em;   
color: transparent;   
transition: color 0.2s 0s, width 0.3s 0.2s;   
}   
.cd-modal-action .cd-modal-bg {   
position: absolute;   
top: 0;   
left: 50%;   
transform: translateX(-2em);   
width: 4em;   
height: 4em;   
background-color: #123758;   
border-radius: 50%;   
opacity: 0;   
visibility: hidden;   
transition: visibility 0s 0.5s;   
}   
.cd-modal-action .cd-modal-bg.is-visible {   
opacity: 1;   
visibility: visible;   
}

var btnRadius = $('.cd-modal-bg').width()/2,   
left = $('.cd-modal-bg').offset().left + btnRadius,   
top = $('.cd-modal-bg').offset().top + btnRadius - $(window).scrollTop(),   
scale = scaleValue(top, left, btnRadius, $(window).height(), $(window).width());   
function scaleValue( topValue, leftValue, radiusValue, windowW, windowH) {   
var maxDistHor = ( leftValue > windowW/2) ? leftValue : (windowW - leftValue),   
maxDistVert = ( topValue > windowH/2) ? topValue : (windowH - topValue);   
return Math.ceil(Math.sqrt( Math.pow(maxDistHor, 2) + Math.pow(maxDistVert, 2) )/radiusValue);   
}