/* 确保所有相关元素使用正确的盒模型 */
.pdf-gallery,
.pdf-card,
.pdf-thumbnail,
.pdf-title {
    box-sizing: border-box;
}

/* PDF缩略图画廊容器 */
.pdf-gallery {
    display: flex;
    justify-content: center;
    flex-wrap: nowrap;
    gap: 30px;
    padding: 20px;
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    overflow: hidden;
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

/* 添加过渡状态类 */
.pdf-gallery.transitioning-in {
    transform: translateX(30px);
    opacity: 0;
}

.pdf-gallery.transition-reset {
    transform: translateX(0);
    opacity: 1;
}

/* 分类标题样式 */
.category-title {
    text-align: center;
    color: #333;
    margin: 30px auto;  /* 增加上下间距 */
    font-weight: normal;
    width: 100%;
    max-width: 1200px;
    padding: 0 20px;
    font-size: 22px;  /* 增加字体大小 */
    letter-spacing: 1px;  /* 添加字间距 */
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);  /* 添加过渡效果 */
    opacity: 0;  /* 初始状态设为透明 */
    transform: translateY(20px);  /* 初始位置向下偏移 */
}

/* 标题的入场效果 */
.category-title.show {
    opacity: 1;
    transform: translateY(0);
}

/* 标题的过渡效果 */
.category-title.transitioning {
    opacity: 0;
    transform: translateX(-30px);
}

/* PDF卡片样式 */
.pdf-card {
    position: relative;
    width: calc(33.333% - 20px);
    min-width: 250px;
    max-width: 300px;  /* 稍微减小最大宽度 */
    border-radius: 15px;
    overflow: hidden;
    cursor: pointer;
    opacity: 0;
    transform: translateX(50px) translateY(-5px);
    transition: all 0.5s cubic-bezier(0.34, 1.56, 0.64, 1);
    box-shadow: 0 12px 24px rgba(0,0,0,0.12),  /* 增强默认阴影 */
                0 4px 8px rgba(0,0,0,0.08),
                0 2px 4px rgba(0,0,0,0.04);
}

.pdf-card.show {
    opacity: 1;
    transform: translateX(0) translateY(-5px);
}

/* 悬停效果 */
.pdf-card:hover {
    transform: translateY(-12px) scale(1.02);
    box-shadow: 0 20px 40px rgba(0,0,0,0.16),  /* 增强悬停时的阴影 */
                0 8px 16px rgba(0,0,0,0.1),
                0 4px 8px rgba(0,0,0,0.06);
}

/* 点击效果 */
.pdf-card:active {
    transform: translateY(-8px) scale(0.98); /* 点击时稍微下沉 */
    box-shadow: 0 10px 25px rgba(0,0,0,0.12);
}

/* 缩略图容器 */
.pdf-thumbnail {
    position: relative;
    width: 100%;
    padding-top: 141.4%;  /* A4纸比例 1:1.414 */
    background-color: #f5f5f5;
    border-radius: 15px;
    overflow: hidden;
}

.pdf-thumbnail canvas,
.pdf-thumbnail img {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    object-fit: contain;  /* 改为 contain 以保持比例 */
    transition: transform 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

/* 毛玻璃标题栏 */
.pdf-title {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    padding: 15px;
    background: rgba(255, 255, 255, 0.5); /* 略微增加透明度 */
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-top: 1px solid rgba(255, 255, 255, 0.4);
    color: #333;
    text-align: center;
    font-weight: 500;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    transition: all 0.3s ease;
}

.pdf-card:hover .pdf-title {
    background: rgba(255, 255, 255, 0.6); /* 悬停时增加不透明度 */
    padding: 18px 15px; /* 悬停时略微增加内边距 */
}

/* 点击时的过渡效果 */
.pdf-gallery.transitioning .pdf-card {
    animation: cardTransition 0.4s cubic-bezier(0.4, 0, 0.2, 1) forwards;
}

@keyframes cardTransition {
    0% {
        transform: translateX(0);
        opacity: 1;
    }
    100% {
        transform: translateX(-30px);
        opacity: 0;
    }
}

/* 加载占位符 */
.loading-placeholder {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    background: #f5f5f5;
}

/* 加载动画 */
.loading-spinner {
    width: 50px;
    height: 50px;
    border: 5px solid #f3f3f3;
    border-top: 5px solid #3498db;
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* 错误状态显示 */
.loading-error {
    color: #e74c3c;
    text-align: center;
    padding: 20px;
}

/* 响应式布局适配 */
@media screen and (max-width: 900px) {
    .pdf-gallery {
        flex-wrap: wrap;
        gap: 20px;
        padding: 15px;
    }
    .pdf-card {
        width: calc(50% - 10px);
        min-width: 160px;
    }
}

@media screen and (max-width: 600px) {
    .pdf-gallery {
        gap: 15px;
        padding: 10px;
        overflow-x: hidden; /* 防止横向滚动 */
    }
    .pdf-card {
        width: calc(33.333% - 10px);
        min-width: 100px;
        max-width: none;
    }
}

@media screen and (max-width: 480px) {
    .pdf-gallery {
        gap: 10px;
        padding: 8px;
    }
    .pdf-card {
        width: calc(50% - 5px);
        min-width: 140px;
    }
}

@media screen and (max-width: 360px) {
    .pdf-gallery {
        gap: 8px;
        padding: 5px;
    }
    .pdf-card {
        width: 100%;
        min-width: auto;
        max-width: 280px;
        margin: 0 auto;
    }
}