*,
*::before,
*::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html, body {
    height: 100%;
}

body {
    font-family: system-ui, -apple-system, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
    background: #ffffff;
    color: #111;
    overflow-x: hidden;
}

/* 固定视频背景，完全不可交互 */
.hero-video {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    object-fit: cover;
    z-index: 0;
    pointer-events: none;
    user-select: none;
    -webkit-user-select: none;
    background: #fff;
}

/* 主内容层，高于视频 */
.content {
    position: relative;
    z-index: 1;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    /* 顶部空白，让视频完全展示不被遮挡 */
    padding-top: 100vh;
}

/* 图片容器：竖排，逐个出现 */
.picture-item {
    width: 100%;
    height: 90vh;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    transform: translateY(40px);
    transition: opacity 0.7s cubic-bezier(0.16, 1, 0.3, 1),
    transform 0.7s cubic-bezier(0.16, 1, 0.3, 1);
    will-change: transform, opacity;
}

.picture-item.visible {
    opacity: 1;
    transform: translateY(0);
}

.picture-item img {
    max-width: 90%;
    max-height: 90%;
    object-fit: contain;
    border-radius: 24px;
    box-shadow: 0 20px 50px rgba(0,0,0,0.08);
    background: #fff;
}

/* 底部大字区域：紧贴底部，无多余空隙 */
.footer-big {
    margin-top: auto;
    width: 100%;
    padding: 0 0 10px 0;
    text-align: center;
    background: transparent;
}

.bye-text {
    font-size: clamp(3rem, 12vw, 8rem);           /* 充满宽度，且保证单行 */
    font-weight: 900;
    line-height: 0.85;
    white-space: nowrap;
    text-transform: uppercase;
    letter-spacing: -0.02em;
    color: #111;
    /* 零动画，纯粹静态 */
}

/* 响应式微调 */
@media (max-width: 600px) {
    .picture-item {
        height: 80vh;
    }
    .bye-text {
        font-size: 22vw;
    }
}