<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Search Animation</title>
    <link rel="stylesheet" href="SearchAnimation.css">
</head>
<body>
    <div class="container">
        <div class="search">
            <span></span>
            <input type="text">
        </div>
    </div>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
    <script>
        $('span').click(function(){
            $('.container').toggleClass('active');
            $('input').toggleClass('active');
            $('span').toggleClass('active');
        });
    </script>
</body>
</html>

.container,input,span {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%,-50%);
}
.container,input,span,span::before{transition: .4s;}
.container {
    width: 100px;
    height: 100px;
    background: dodgerblue;
    border-radius: 100%;
    overflow: hidden;
}
input{
    font-family: verdana;
    font-size: 1.3em;
    color: white;
    width: 35px;
    height: 35px;
    background: transparent;
    border-radius: 100%;
    z-index: -1;
    border: 0px solid white;
}
span {
    background: transparent;
    width: 35px;
    height: 35px;
    border-radius: 100%;
    border: 3px solid white;
}
span::before {
    content: "";
    position: absolute;
    width: 3px;
    background: white;
    height: 20px;
    top: 28px;
    left: 35px;
    transform: rotate(-45deg);
    z-index: 3;
}
.search{cursor: pointer;}
.container.active {
    width: 100%;
    height: 100vh;
    border-radius: 0px;
}
span.active {
    transform: scale(.6);
    margin-left: 130px;
    margin-top: -20px;
}
input.active {
    width: 300px;
    height: 50px;
    border-width: 3px;
    border-radius: 40px;
    padding: 0 50px 0 10px;
    outline: none;
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.