<div class="container">
<div class="row text-center">
        <div class="col-lg-12">
            <form>
                <h2>Subscribe</h2>
                <div class="form-group margin-below">
                    <input type="email" class="form-control" id="email" aria-describedby="Email"
                           placeholder="Email">
                </div>
                <button type="submit" class="btn2 btn-primary">Sign up</button>
            </form>
        </div>
    </div>
</div>
label, select, button, input[type="submit"], input[type="radio"], input[type="checkbox"] input[type="button"] {
    cursor: pointer;
}
body {
 background: #bdc3c7; /* fallback for old browsers */
  background: -webkit-linear-gradient(to right, #a8edea 0%, #fed6e3 100%); /* Chrome 10-25, Safari 5.1-6 */
  background: linear-gradient(to right, #a8edea 0%, #fed6e3 100%); /* W3C, IE 10+/ Edge, Firefox 16+, Chrome 26+, Opera 12+, Safari 7+ */
}
h2{
    text-align: center;
    margin-bottom: 1.8rem;
}
form {
    background: #f7f4ff;
    border-radius: .3rem;
    padding: 1.3rem;
    width: 350px;
    margin: 2rem auto;
    box-shadow: 12px 12px 5px 0px rgba(0, 0, 0, .08);
}
input {
    width: 100%;
    background: #f5f5f5;
    border: 0;
    padding: 20px;
    border-radius: 8px;
    margin-bottom: 10px;
    border: 1px solid #eee;
}
.btn2 {
    width: 100%;
    padding: 12px;
    border: 0;
    background: #c3b6e2;
    font-size: 1.1em;
    color: #fff;
    text-shadow: 1px 1px 0px rgba(0, 0, 0, .4);
    box-shadow: 0px 3px 0px #ac9ad7;
    margin-top: 1.2rem;
    border-radius: .25rem;
}
.btn2:hover {
    color: #fff;
    background: #8a70c6;
    border-color: #a18cd1;
}
.form-control {
    display: block;
    width: 100%;
    padding: .5rem .75rem;
    font-size: 1rem;
    line-height: 1.25;
    color: #55595c;
    background-color: #f9f9f9;
    background-image: none;
    -webkit-background-clip: padding-box;
    background-clip: padding-box;
    border: 1px solid rgba(0,0,0,.15);
    border-radius: .25rem;
}
.margin-below{
    margin-bottom: 1.2rem;
}
.form-control:focus {
    border-color: #7743ff;
    box-shadow: inset 0 1px 1px rgba(45, 45, 45, 0.07), 0 0 8px rgba(129, 129, 129, 0.6);
}

External CSS

  1. https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.1.3/css/bootstrap.min.css

External JavaScript

This Pen doesn't use any external JavaScript resources.