.course-thumbnail {
    position: relative;
    width: 100%;
    padding-top: 56.25%; /* 16:9 Aspect Ratio */
    overflow: hidden;
    border-radius: 8px;
}

.course-thumbnail img {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform 0.3s ease;
}

.course-card:hover .course-thumbnail img {
    transform: scale(1.05);
}

.play-button {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    z-index: 2;
    opacity: 0;
    transition: all 0.3s ease;
    filter: drop-shadow(0 2px 4px rgba(0, 0, 0, 0.3));
}

.play-button svg {
    width: 64px;
    height: 64px;
    transition: transform 0.3s ease;
}

.course-card:hover .play-button {
    opacity: 1;
}

.course-card:hover .play-button svg {
    transform: scale(1.1);
}

/* 确保播放按钮在课程徽章之上 */
.course-overlay {
    z-index: 1;
}

.play-button {
    z-index: 2;
}

/* 添加一个半透明的遮罩层，让播放按钮更显眼 */
.course-thumbnail::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0);
    transition: background-color 0.3s ease;
    z-index: 1;
}

.course-card:hover .course-thumbnail::after {
    background: rgba(0, 0, 0, 0.2);
}

.course-card-link {
    text-decoration: none;
    color: #333;
    display: block;
    transition: all 0.3s ease;
}

.course-card-link:hover {
    text-decoration: none;
    color: #0f6cbf;
}

.course-card-link:hover .course-title {
    color: #0f6cbf;
}

.course-card-link .course-title {
    color: #333;
    transition: color 0.3s ease;
    margin: 0;
    font-size: 1rem;
    line-height: 1.4;
    /* 文本超出两行显示省略号 */
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
    text-overflow: ellipsis;
}

.course-card-link .course-meta {
    color: #666;
    font-size: 0.875rem;
    margin-top: 0.5rem;
}

.course-card-link:hover .course-meta {
    color: #666;
}