:root {
    --input-padding-x: .75rem;
    --input-padding-y: .75rem;
}

html,
body {
    height: 100%;
}

body {
    display: -ms-flexbox;
    display: -webkit-box;
    display: flex;
    -ms-flex-align: center;
    -ms-flex-pack: center;
    -webkit-box-align: center;
    align-items: center;
    -webkit-box-pack: center;
    justify-content: center;
    padding-top: 40px;
    padding-bottom: 40px;
    background-color: #f5f5f5;
}

.form-signin {
    width: 100%;
    max-width: 420px;
    padding: 15px;
    margin: 0 auto;
}

.form-label-group {
    position: relative;
    margin-bottom: 1rem;
}

    .form-label-group > input,
    .form-label-group > label {
        padding: var(--input-padding-y) var(--input-padding-x);
    }

    .form-label-group > label {
        position: absolute;
        top: 0;
        left: 0;
        display: block;
        width: 100%;
        margin-bottom: 0; /* Override default `<label>` margin */
        line-height: 1.5;
        color: #495057;
        border: 1px solid transparent;
        border-radius: .25rem;
        transition: all .1s ease-in-out;
    }

    .form-label-group input::-webkit-input-placeholder {
        color: transparent;
    }

    .form-label-group input:-ms-input-placeholder {
        color: transparent;
    }

    .form-label-group input::-ms-input-placeholder {
        color: transparent;
    }

    .form-label-group input::-moz-placeholder {
        color: transparent;
    }

    .form-label-group input::placeholder {
        color: transparent;
    }

    .form-label-group input:not(:placeholder-shown) {
        padding-top: calc(var(--input-padding-y) + var(--input-padding-y) * (2 / 3));
        padding-bottom: calc(var(--input-padding-y) / 3);
    }

        .form-label-group input:not(:placeholder-shown) ~ label {
            padding-top: calc(var(--input-padding-y) / 3);
            padding-bottom: calc(var(--input-padding-y) / 3);
            font-size: 12px;
            color: #777;
        }