.back-to-top-btn {
    position: fixed;
    right: var(--spacing-4);
    bottom: var(--spacing-4);
    z-index: var(--z-sticky);
    display: flex;
    width: 44px;
    min-width: 44px;
    height: 44px;
    align-items: center;
    justify-content: center;
    padding: 0;
    border: 1px solid var(--color-border-strong);
    border-radius: 0;
    background: var(--color-bg);
    color: var(--color-text);
    opacity: 0;
    pointer-events: none;
    transform: translateY(8px);
    transition:
        opacity var(--transition-base),
        transform var(--transition-base);
}

.back-to-top-btn.visible {
    opacity: 1;
    pointer-events: auto;
    transform: translateY(0);
}

.back-to-top-btn:hover {
    border-color: var(--color-primary);
    background: var(--color-primary);
    color: var(--color-text-contrast);
}

.back-to-top-btn .icon {
    width: 1.2rem;
    height: 1.2rem;
}