/* 课程页面样式 */

/* 筛选标签 */
.course-filter {
    background-color: white;
    border-bottom: 1px solid var(--border-color);
    padding: 20px 0;
    position: sticky;
    top: 70px;
    z-index: 100;
}

.filter-tabs {
    display: flex;
    gap: 15px;
    justify-content: center;
    flex-wrap: wrap;
}

.filter-btn {
    padding: 10px 24px;
    border: 2px solid var(--border-color);
    background-color: white;
    border-radius: 25px;
    cursor: pointer;
    font-size: 15px;
    font-weight: 500;
    color: var(--dark-text);
    transition: all 0.3s;
}

.filter-btn:hover {
    border-color: var(--primary-blue);
    color: var(--primary-blue);
}

.filter-btn.active {
    background-color: var(--primary-blue);
    border-color: var(--primary-blue);
    color: white;
}

/* 课程列表 */
.course-list {
    padding: 50px 0;
    background-color: var(--light-bg);
}

.course-section {
    margin-bottom: 60px;
    scroll-margin-top: 130px;
}

.course-section .section-title {
    text-align: left;
    font-size: 28px;
    margin-bottom: 8px;
    padding-left: 10px;
    border-left: 4px solid var(--accent-yellow);
}

.course-section .section-subtitle {
    font-size: 14px;
    color: var(--text-light);
    margin-bottom: 24px;
    padding-left: 14px;
    line-height: 1.6;
}

.course-section .level-title {
    font-size: 18px;
    font-weight: 700;
    color: var(--primary);
    margin: 32px 0 16px;
    padding-left: 12px;
    border-left: 3px solid var(--accent);
}

.course-grid {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 24px;
}

.course-grid .course-card {
    flex: 0 1 calc(25% - 18px);
    min-width: 260px;
    max-width: 320px;
}

.course-card {
    background-color: white;
    border-radius: 12px;
    overflow: hidden;
    box-shadow: 0 4px 15px rgba(0,0,0,0.08);
    transition: transform 0.3s, box-shadow 0.3s;
}

.course-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 12px 30px rgba(0,0,0,0.12);
}

.course-image {
    height: 160px;
    position: relative;
    display: flex;
    align-items: center;
    justify-content: center;
}

.a1-bg {
    background: linear-gradient(135deg, #1E4D8C 0%, #3D7EB8 100%);
}

.a2-bg {
    background: linear-gradient(135deg, #3D7EB8 0%, #5BA3D0 100%);
}

.b1-bg {
    background: linear-gradient(135deg, #F5B71B 0%, #F9D26A 100%);
}

.grammar-bg {
    background: linear-gradient(135deg, #2C3E50 0%, #4A6274 100%);
}

.course-level {
    position: absolute;
    top: 12px;
    left: 12px;
    background-color: rgba(255,255,255,0.95);
    padding: 5px 12px;
    border-radius: 20px;
    font-weight: 700;
    font-size: 14px;
}

.a1-bg .course-level { color: #1E4D8C; }
.a2-bg .course-level { color: #3D7EB8; }
.b1-bg .course-level { color: #F5B71B; }
.grammar-bg .course-level { color: #2C3E50; }

.course-lessons {
    position: absolute;
    bottom: 12px;
    right: 12px;
    background-color: rgba(0,0,0,0.6);
    color: white;
    padding: 4px 10px;
    border-radius: 4px;
    font-size: 12px;
}

.course-content {
    padding: 20px;
}

.course-content h3 {
    font-size: 18px;
    margin-bottom: 10px;
    color: var(--dark-text);
}

.course-content p {
    font-size: 14px;
    color: var(--light-text);
    line-height: 1.6;
    margin-bottom: 15px;
    height: 65px;
    overflow: hidden;
}

.course-meta {
    display: flex;
    gap: 15px;
    margin-bottom: 15px;
    font-size: 13px;
    color: var(--light-text);
}

.course-content .btn {
    width: 100%;
    text-align: center;
    padding: 10px;
    font-size: 14px;
}

/* 响应式设计 */
@media (max-width: 1200px) {
    .course-grid .course-card {
        flex: 0 1 calc(33.333% - 16px);
    }
}

@media (max-width: 900px) {
    .course-grid .course-card {
        flex: 0 1 calc(50% - 12px);
    }
}

@media (max-width: 768px) {
    .page-header h1 {
        font-size: 32px;
    }
    
    .filter-tabs {
        gap: 10px;
    }
    
    .filter-btn {
        padding: 8px 16px;
        font-size: 14px;
    }
}

@media (max-width: 560px) {
    .course-grid .course-card {
        flex: 1 1 100%;
        max-width: 100%;
    }
    
    .course-section .section-title {
        font-size: 24px;
    }
}