.back-to-top {
    position: fixed;
    right: max(20px, env(safe-area-inset-right));
    bottom: max(20px, env(safe-area-inset-bottom));
    z-index: 90;
    display: flex;
    align-items: center;
    justify-content: center;
    width: 48px;
    height: 48px;
    padding: 0;
    border: 1px solid #ea913f;
    border-radius: 50%;
    background: #b8550f;
    color: #fff;
    box-shadow: 0 3px 12px #0005;
    cursor: pointer;
}
.back-to-top[hidden] { display: none; }
.back-to-top:hover { background: #984509; }
.back-to-top:focus-visible { outline: 3px solid #fdb46b; outline-offset: 3px; }