/* --- 全局与基础样式 --- */
:root {
    --primary-color: #0c3d7a; /* 深蓝 */
    --secondary-color: #d4af37; /* 金色 */
    --background-color: #f0f2f5; /* 淡灰背景 */
    --sidebar-bg: #ffffff;
    --card-bg: #ffffff;
    --text-primary: #333333;
    --text-secondary: #666666;
    --border-color: #e5e7eb;
    --shadow-light: 0 4px 6px -1px rgba(0, 0, 0, 0.05), 0 2px 4px -2px rgba(0, 0, 0, 0.05);
    --shadow-medium: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.1);
    --header-height: 101px; /* 定义一个头部高度变量 */
}

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

body {
    font-family: 'Noto Sans SC', sans-serif;
    background-color: var(--background-color);
    color: var(--text-primary);
    overflow: hidden; /* 防止页面滚动 */
}

.app-container {
    display: flex;
    height: 100vh;
}

/* --- 左侧导航栏 (Sidebar) --- */
.sidebar {
    width: 320px; /* 稍微加宽以适应中英文 */
    flex-shrink: 0;
    background-color: var(--sidebar-bg);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    box-shadow: var(--shadow-light);
}

.logo-container {
    padding: 24px;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: center;
    align-items: center;
}

.logo {
    max-width: 80%;
    height: auto;
}

.university-nav {
    flex-grow: 1;
    overflow-y: auto;
    padding: 16px 0;
}
.university-nav::-webkit-scrollbar {
    width: 6px;
}
.university-nav::-webkit-scrollbar-thumb {
    background: #ccc;
    border-radius: 3px;
}

.nav-category-title {
    padding: 12px 24px;
    font-size: 0.8rem;
    font-weight: 700;
    color: var(--secondary-color);
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-top: 16px;
    border-bottom: 1px solid var(--border-color);
}
.nav-category-title:first-child {
    margin-top: 0;
}

.nav-item {
    display: flex;
    flex-direction: column;
    padding: 12px 24px;
    color: var(--text-secondary);
    text-decoration: none;
    transition: all 0.3s ease;
    border-left: 4px solid transparent;
    cursor: pointer;
}

.nav-item .uni-en {
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--text-primary);
}

.nav-item .uni-zh {
    font-size: 0.85rem;
    color: var(--text-secondary);
}

.nav-item:hover {
    background-color: #f8f9fa;
    border-left-color: var(--secondary-color);
}

.nav-item.active {
    background-color: #e9ecef;
    border-left-color: var(--primary-color);
}

.nav-item.active .uni-en {
    font-weight: 700;
    color: var(--primary-color);
}

/* --- 右侧主内容区 (Main Content) --- */
.main-content {
    flex-grow: 1;
    display: flex;
    flex-direction: column;
    overflow-y: auto;
}

.main-header {
    padding: 24px 40px;
    border-bottom: 1px solid var(--border-color);
    background-color: var(--card-bg);
    position: sticky;
    top: 0;
    z-index: 10;
    min-height: var(--header-height); /* 确保头部有最小高度 */
}

#main-title {
    font-size: 2rem;
    font-weight: 700;
    color: var(--primary-color);
}

.main-subtitle {
    font-size: 1rem;
    color: var(--text-secondary);
    margin-top: 4px;
}

/* --- 筛选器样式 (已更新) --- */
.filters-container {
    padding: 16px 40px;
    background-color: #f8f9fa;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    gap: 16px;
    position: sticky; /* 设置为置顶 */
    top: var(--header-height); /* 使用变量确保在header下方 */
    z-index: 9; /* z-index低于header */
}

.filter-group {
    display: flex;
    align-items: center;
    gap: 12px;
    flex-wrap: wrap;
}

.filter-label {
    font-weight: 700;
    color: var(--primary-color);
    font-size: 0.9rem;
    flex-shrink: 0;
}

.filter-btn {
    padding: 6px 16px;
    border: 1px solid var(--border-color);
    background-color: #fff;
    color: var(--text-secondary);
    border-radius: 20px;
    cursor: pointer;
    transition: all 0.3s ease;
    font-size: 0.85rem;
}

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

.filter-btn.active {
    background-color: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
    font-weight: 700;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}


.pathway-details-grid {
    padding: 40px;
    display: flex;
    flex-direction: column;
    gap: 32px;
}

/* --- 欢迎/无结果占位符 --- */
.welcome-placeholder, .no-results-placeholder {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    min-height: 40vh;
    color: #ccc;
    text-align: center;
}
.placeholder-icon {
    font-size: 5rem;
    margin-bottom: 24px;
}
.welcome-placeholder p, .no-results-placeholder p {
    font-size: 1.5rem;
    font-weight: 300;
}


/* --- 课程详情卡片 --- */
.pathway-card {
    background-color: var(--card-bg);
    border-radius: 12px;
    box-shadow: var(--shadow-medium);
    overflow: hidden;
    opacity: 0;
    transform: translateY(20px);
    animation: fadeIn 0.5s ease-out forwards;
}

@keyframes fadeIn {
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.card-header {
    background: linear-gradient(135deg, var(--primary-color), #1a5ba8);
    color: white;
    padding: 24px;
}

.course-title-main {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: 4px;
}
.course-title-sub {
    font-size: 1.1rem;
    font-weight: 400;
    opacity: 0.9;
}

.tags-container {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-top: 16px;
}

.tag {
    background-color: rgba(255, 255, 255, 0.2);
    color: white;
    padding: 4px 12px;
    border-radius: 16px;
    font-size: 0.8rem;
    font-weight: 500;
}

.tag.highlight {
    background-color: var(--secondary-color);
    color: var(--primary-color);
}

.card-body {
    padding: 24px;
}

.info-section {
    margin-bottom: 24px;
}
.info-section:last-child {
    margin-bottom: 0;
}

.section-title {
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 12px;
    padding-bottom: 8px;
    border-bottom: 2px solid var(--secondary-color);
    display: inline-block;
}

.pathway-description {
    font-size: 1rem;
    line-height: 1.6;
    background-color: #f8f9fa;
    padding: 16px;
    border-radius: 8px;
    border-left: 4px solid var(--primary-color);
}

.university-programs-list {
    list-style: none;
    padding-left: 0;
    column-count: 2;
    column-gap: 24px;
}

.program-item {
    padding: 8px 0;
    border-bottom: 1px solid var(--border-color);
    font-size: 0.95rem;
}
.program-item:before {
    content: '🎓';
    margin-right: 8px;
}

/* --- 响应式设计 --- */
@media (max-width: 1024px) {
    .university-programs-list {
        column-count: 1;
    }
    :root {
        --header-height: 85px; /* 调整小屏幕下的头部高度 */
    }
}

@media (max-width: 768px) {
    .app-container {
        flex-direction: column;
    }
    .sidebar {
        width: 100%;
        height: auto;
        max-height: 40vh;
        border-right: none;
        border-bottom: 1px solid var(--border-color);
    }
    .main-content {
        height: 60vh;
    }
    .pathway-details-grid {
        padding: 24px;
    }
    .main-header {
        padding: 16px 24px;
        min-height: auto;
    }
    #main-title {
        font-size: 1.5rem;
    }
    .filters-container {
        padding: 16px 24px;
        position: static; /* 在移动端取消置顶，以获得更好体验 */
    }
}