/* 回到顶部浮动按钮。当前仅信念页加载（长页面有滚动需求）。 */

.back-to-top {
    position: fixed;
    right: 24px;
    bottom: 24px;
    width: 44px;
    height: 44px;
    border-radius: 50%;
    background: var(--white);
    color: var(--green);
    box-shadow: 0 4px 16px rgba(0,0,0,0.12);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 22px;
    line-height: 1;
    cursor: pointer;
    border: none;
    opacity: 0;
    pointer-events: none;
    transform: translateY(8px);
    transition: opacity 0.3s ease, transform 0.3s ease, box-shadow 0.2s ease;
    z-index: 999;
}

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

.back-to-top:hover {
    box-shadow: 0 8px 24px rgba(0,0,0,0.18);
    transform: translateY(-2px);
    color: var(--green-dark);
}

.back-to-top:active {
    transform: translateY(0);
}

@media (max-width: 600px) {
    .back-to-top {
        right: 16px;
        bottom: 16px;
        width: 40px;
        height: 40px;
        font-size: 20px;
    }
}