#back-to-top {
    position: fixed;
    right: 16px;
    bottom: 16px;
    right: calc(16px + env(safe-area-inset-right));
    bottom: calc(16px + env(safe-area-inset-bottom));
    z-index: 90;
    display: flex;
    align-items: center;
    justify-content: center;
    box-sizing: border-box;
    width: 48px;
    height: 48px;
    padding: 0;
    border: 2px solid #fff;
    border-radius: 50%;
    background: #9b30b5;
    color: #fff;
    box-shadow: 0 3px 10px rgba(0, 28, 47, .3);
    cursor: pointer;
}

#back-to-top[hidden] {
    display: none;
}

#back-to-top:hover {
    background: #85249d;
}

#back-to-top:focus {
    outline: 2px solid #2980b9;
    outline-offset: 2px;
}