body, html {
    margin: 0;
    padding: 0;
    width: 100%;
    height: 100%;
    overflow-x: hidden;
    cursor: pointer; /* 全頁點擊手勢 */
}

.container {
    width: 100%;
    display: flex;
    flex-direction: column;
    align-items: center;
    position: relative;
    padding-bottom: 20px; /* 底部留白 */
}

.bg-image {
    width: 100%;
    height: auto;
    display: block;
}

.button-container {
    position: fixed;
    bottom: 20px;
    left: 50%;
    transform: translateX(-50%);
    z-index: 10;
    width: 80%;
    max-width: 300px; /* 限制按鈕最大寬度 */
    transition: transform 0.2s;
}

.btn-img {
    width: 100%;
    height: auto;
    filter: drop-shadow(0 4px 6px rgba(0,0,0,0.3));
}

.button-container:active {
    transform: translateX(-50%) scale(0.95);
}

/* RWD 微調: 在大螢幕上限制容器最大寬度，避免圖片過大 */
@media (min-width: 768px) {
    .container {
        max-width: 768px;
        margin: 0 auto;
    }
}