input with floating label

by gbos

HTML

<input required />
<label><span>Name</span></label>

CSS

input {
    display: block;
    border: 0;
    outline: none;
    box-shadow: none;
    margin-top: 20px;
    opacity: 0;
    transition: opacity 0.3s;
}

label {
    position: relative;
    max-height: 0px;
    display: block;
    border-top: 1px solid grey;
}

label>span {
    position: absolute;
    top: -20px;
    z-index: -1;
    transition: top 0.3s, font-size 0.3s;
}

input:focus,
input:valid {
    opacity: 1;
    outline: none;
}

input:valid+label>span,
input:focus+label>span {
    position: absolute;
    top: -30px;
    font-size: 70%;
    color: blue;
}