Jazzy CSS Checkbox

html,
body {
    height: 100%;
}
body {
    font: 600 20px/3em sans-serif;
    position: relative;
}
input[type="checkbox"] {
    opacity: 0;
    position: absolute;
    left: 0;
    bottom: 100%;
}
.check {
    background-color: salmon;
    background-clip: padding-box;
    color: snow;
    display: block;
    padding: 0 2.5em;
    overflow: hidden;
    position: absolute;
    top: 50%;
    left: 50%;
    white-space: nowrap;
    cursor: pointer;
    user-select: none;
    border-radius: .375em;
    transform: translate3d(-50%, -50%, 0);
    transition: all .15s ease-in-out .1s;
    input[type="checkbox"]:focus + &,
    input[type="checkbox"]:checked:focus + & {
        box-shadow: 0 0 0 .3em rgba(black, .2);
    }
    input[type="checkbox"]:checked + & {
        background-color: darkseagreen;
        padding-right: 1.5em;
        padding-left: 3.5em;
    }
    &:before {
        content: "✔";
        font-size: 1.5em;
        position: absolute;
        top: 0;
        left: 1em;
        transform: translateX(-2em);
        transition: all .15s ease-in-out;
    }
    input[type="checkbox"]:checked + &:before {
        transform: none;
        transition: all .25s ease-in-out;
    }
}