SL1de,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style>
.content__text {
font-size: 18px;
line-height: 26px;
font-family: Kazimir,'Helvetica CY',Arial,sans-serif;
position: relative;
color: #333;
}
.content__text-wrap {
margin-bottom: 20px;
max-height: 400px;
overflow: hidden;
}
.open .content__text-wrap {
max-height: none;
}
.open.content__text.shadow:after {
opacity: 0;
transition: 0s;
}
.content__text.shadow:after {
transition: .8s;
display: block;
position: absolute;
left: 0;
right: 0;
top: 0;
height: 400px;
content: ' ';
pointer-events: none;
background: -moz-linear-gradient(top,rgba(255,255,255,0) 0,rgba(255,255,255,0) 1%,rgba(255,255,255,0) 70%,#fff 100%);
background: -webkit-linear-gradient(top,rgba(255,255,255,0) 0,rgba(255,255,255,0) 1%,rgba(255,255,255,0) 70%,#fff 100%);
background: linear-gradient(to bottom,rgba(255,255,255,0) 0,rgba(255,255,255,0) 1%,rgba(255,255,255,0) 70%,#fff 100%);
filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#ffffff', endColorstr='#ffffff', GradientType=0);
}
.product__button {
max-width: 176px;
margin: 0 auto 31px;
padding: 10px;
border: 1px solid #999;
border-radius: 3px;
font-family: GraphikCy-Medium,'Helvetica CY',Arial,sans-serif;
font-size: 14px;
line-height: 14px;
text-align: center;
cursor: pointer;
display: block;
}
.product__button:after {
content: 'Развернуть';
}
.open .product__button:after {
content: 'Свернуть';
}
</style>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script>
$(function() {
$('.content__text').on('click', '.toggle' ,function() {
$(this).parents('.content__text').toggleClass('open')
})
});
</script>
</head>
<body>
<div class="firstbl content__text shadow">
<div class="content content__text-wrap ">
<div>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Repellendus accusamus hic quae libero rem odit et fugit cumque dolore perferendis tempore officia illum atque nam, quia ut, quibusdam. Modi, ex.</div>
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<div>Eligendi ut recusandae officiis nostrum praesentium modi error, quae ab velit itaque, beatae reprehenderit delectus unde id facere aliquam totam est facilis culpa expedita aspernatur! Et amet omnis porro exercitationem.</div>
<div>Fugit quisquam asperiores impedit ipsa, doloribus officiis maiores? Dolore possimus tenetur eum. Corrupti repudiandae doloribus officiis accusamus soluta fugiat consequatur hic, distinctio perferendis. Ipsum incidunt, magni veniam recusandae illum cupiditate.</div>
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<div>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Accusamus iusto soluta quibusdam, pariatur molestiae est. Provident impedit unde alias dolores rerum ex minus quae ab, et nihil similique fugit optio.</div>
<div>Hic odit, adipisci. Nam quia dolor architecto debitis. Possimus dolor impedit excepturi quidem. Aperiam neque aut voluptatibus sit earum sint, libero consectetur repellendus doloremque architecto qui, suscipit autem est magnam.</div>
</div>
<div class="toggle product__button"></div>
</div>
</body>
</html>