CSS resize
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>CSS: resize</title>
<style>
div {
border: 1px solid gray;
padding: 20px;
min-width: 50px;
min-height:50px;
}
.first { width:200px; height:100px; }
.second { width:100px; height:50px; }
.third { width:150px; height:80px; }
.resizible {
resize: both;
overflow: auto;
float:left;
}
</style>
</head>
<body>
<div class="first resizible"></div>
<div class="second resizible"></div>
<div class="third resizible"></div>
</body>
</html>
Всемирная паутина
Пример
Flexbox Froggy
