/* 全站「返回頁頂」浮動按鈕 */
.scroll-top {
    position: fixed;
    right: var(--space-md);
    bottom: calc(var(--space-md) + env(safe-area-inset-bottom, 0px));
    z-index: 90;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 2.75rem;
    height: 2.75rem;
    padding: 0;
    border: none;
    border-radius: 50%;
    background: var(--color-primary);
    color: var(--color-white);
    box-shadow: var(--shadow-md);
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
    transition: opacity var(--transition), visibility var(--transition), background var(--transition), transform var(--transition);
}

.scroll-top.is-visible {
    opacity: 1;
    visibility: visible;
    pointer-events: auto;
}

.scroll-top:hover {
    background: var(--color-primary-dark);
    transform: translateY(-0.125rem);
}

.scroll-top__icon {
    width: 1.25rem;
    height: 1.25rem;
    flex-shrink: 0;
}