:root {
    --primary-blue: #007bff;
    --secondary-blue: #e7f3ff;
    --text-color: #343a40;
    --light-text-color: #6c757d;
    --background-color: #f8f9fa;
    --border-color: #dee2e6;
    --hot-red: #dc3545;
    --score-green: #28a745;
    --white-color: #fff;
    --link-color: #0056b3;
    --text-secondary: #4b5563;
    --success-color: #16a34a;
    --danger-color: #dc2626;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    line-height: 1.6;
    margin: 0;
    background-color: var(--background-color);
    color: var(--text-color);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

main {
    flex: 1;
}

.container {
    max-width: 900px;
    margin: 20px auto;
    padding: 0 15px;
}

.main-content-card, .teacher-details {
    background: var(--white-color);
    padding: 30px;
    border-radius: 12px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.08);
    margin-bottom: 20px;
}

.home-header {
    background: linear-gradient(135deg, var(--primary-blue), #0056b3);
    color: var(--white-color);
    padding: 2rem 1.5rem;
    text-align: center;
    border-radius: 8px;
    margin-bottom: 25px;
}

.home-header h1 { margin: 0; font-size: 2.2em; }
.home-header p { opacity: 0.9; margin-top: 5px; }


.search-container { position: relative; }

#teacherSearch {
    width: 100%;
    padding: 12px 15px;
    font-size: 16px;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    box-sizing: border-box;
    transition: border-color 0.2s, box-shadow 0.2s;
}

#teacherSearch:focus {
    border-color: var(--primary-blue);
    box-shadow: 0 0 0 3px rgba(0, 123, 255, 0.25);
    outline: none;
}

.suggestions-container {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background-color: var(--white-color);
    border: 1px solid var(--border-color);
    border-top: none;
    border-radius: 0 0 6px 6px;
    box-shadow: 0 4px 8px rgba(0,0,0,0.1);
    z-index: 1000;
    max-height: 320px;
    overflow-y: auto;
}

.suggestion-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 12px 15px;
    cursor: pointer;
    text-decoration: none;
    color: inherit;
    border-bottom: 1px solid #f1f1f1;
}

.suggestion-item:last-child { border-bottom: none; }
.suggestion-item:hover { background-color: var(--secondary-blue); }
.teacher-name { font-weight: bold; font-size: 1.1em; color: var(--link-color); }
.teacher-dept { font-size: 0.9em; color: var(--light-text-color); }
.teacher-score { font-size: 1.1em; font-weight: bold; color: var(--score-green); }

.back-link {
    display: inline-block;
    margin-bottom: 20px;
    color: var(--link-color);
    text-decoration: none;
}
.teacher-details h1 {
    font-size: 2.2em;
    color: var(--text-color);
    margin-top: 0;
    margin-bottom: 25px;
}

.teacher-info-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 20px;
    background-color: var(--secondary-blue);
    padding: 20px;
    border-radius: 8px;
    margin-bottom: 30px;
}

.info-item { text-align: center; }
.info-label { font-size: 0.9em; color: var(--light-text-color); display: block; margin-bottom: 5px; }
.info-value { font-size: 1.5em; font-weight: 600; }
.info-value.hot { color: var(--hot-red); }
.info-value.score { color: var(--score-green); }

.gpa-section, .comment-list { margin-top: 40px; }

h2 {
    font-size: 1.6em;
    color: var(--text-color);
    border-bottom: 2px solid var(--primary-blue);
    padding-bottom: 10px;
    margin-bottom: 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.sort-options { font-size: 0.7em; font-weight: normal; }
.sort-options a {
    text-decoration: none;
    padding: 6px 12px;
    border-radius: 5px;
    margin-left: 10px;
    transition: background-color 0.2s;
    color: var(--link-color);
    background-color: var(--secondary-blue);
}
.sort-options a:hover { background-color: #d1e7ff; }

.comment-item {
    background-color: var(--white-color);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 20px;
    margin-bottom: 15px;
    box-shadow: 0 1px 4px rgba(0,0,0,0.04);
}

.comment-content {
    white-space: pre-line;
    margin-bottom: 15px;
    line-height: 1.7;
}

.comment-meta {
    font-size: 0.85em;
    color: var(--light-text-color);
    text-align: right;
    display: flex;
    justify-content: flex-end;
    align-items: center;
    gap: 15px;
}

.comment-meta .likes { color: var(--hot-red); font-weight: 500; }

.gpa-table { width: 100%; border-collapse: collapse; margin-top: 20px; }
.gpa-table th, .gpa-table td { border: 1px solid var(--border-color); padding: 12px; text-align: left; }
.gpa-table th { background-color: var(--secondary-blue); font-weight: 600; }
.gpa-table .course-name { color: var(--link-color); cursor: pointer; }

.compare-table { width: 100%; border-collapse: collapse; }
.compare-table th { text-align: left; color: var(--text-secondary); font-weight: 600; }
.compare-table td, .compare-table th { padding: 8px 10px; border-top: 1px solid var(--border-color); }
.compare-table a.teacher-link { color: var(--text-secondary); font-weight: 500; text-decoration: none; }
.compare-table a.teacher-link:hover { color: var(--link-color); text-decoration: underline; }
.gpa-value { font-weight: 700; }
.gpa-high { color: var(--success-color); }
.gpa-mid { color: var(--link-color); }
.gpa-low { color: var(--danger-color); }
.toggle-compare { background: transparent; border: 1px solid var(--border-color); border-radius: 6px; padding: 4px 10px; color: var(--text-secondary); cursor: pointer; }
.toggle-compare:hover { border-color: var(--link-color); color: var(--link-color); }
.compare-row { display: none; }
.compare-container .compare-loading { display: none; }
.compare-container .compare-error { display: none; color: #c00; }

.footer {
    margin-top: auto;
    padding: 20px 0;
    border-top: 1px solid var(--border-color);
    text-align: center;
    background-color: var(--background-color);
}

.footer-content {
    color: var(--light-text-color);
    font-size: 0.9em;
}

.footer-content p {
    margin: 0;
}

.github-link {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    color: var(--link-color);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.2s;
}

.github-link:hover {
    color: #003d82;
}

.github-icon {
    flex-shrink: 0;
}

/* 返回顶部按钮样式 */
.back-to-top {
    position: fixed;
    top: 95%;
    right: calc((100vw - 900px) / 2 - 90px);
    transform: translateY(-50%);
    width: 50px;
    height: 50px;
    background-color: var(--primary-blue);
    color: var(--white-color);
    border: none;
    border-radius: 50%;
    cursor: pointer;
    display: none;
    align-items: center;
    justify-content: center;
    box-shadow: 0 4px 12px rgba(0, 123, 255, 0.3);
    transition: all 0.3s ease;
    z-index: 1000;
}

.back-to-top:hover {
    background-color: #0056b3;
    transform: translateY(-50%) translateX(-5px);
    box-shadow: 0 6px 16px rgba(0, 123, 255, 0.4);
}

.back-to-top:active {
    transform: translateY(-50%) translateX(0);
}

.back-to-top svg {
    transition: transform 0.2s ease;
}

.back-to-top:hover svg {
    transform: translateY(-1px);
}

@media (max-width: 1000px) {
    .back-to-top {
        right: 20px;
        top: auto;
        bottom: 30px;
        transform: none;
    }
    
    .back-to-top:hover {
        transform: translateY(-2px);
    }
    
    .back-to-top:active {
        transform: translateY(0);
    }
}