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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    padding: 20px;
    line-height: 1.6;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    background: white;
    border-radius: 15px;
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.1);
    overflow: hidden;
}

header {
    background: #2c3e50;
    color: white;
    padding: 30px;
    text-align: center;
}

header h1 {
    margin-bottom: 10px;
    font-size: 2.5em;
}

header p {
    opacity: 0.9;
    font-size: 1.1em;
}

.topic-selection,
.viva-session {
    padding: 40px;
}

.topic-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 20px;
    margin-top: 30px;
}

.topic-card {
    background: #f8f9fa;
    padding: 25px;
    border-radius: 10px;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s ease;
    border: 2px solid #e9ecef;
}

.topic-card:hover {
    transform: translateY(-5px);
    border-color: #3498db;
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
}

.topic-card h3 {
    color: #2c3e50;
    margin-bottom: 10px;
}

.topic-card p {
    color: #7f8c8d;
    font-size: 0.9em;
}

.hidden {
    display: none;
}

.session-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 30px;
    padding-bottom: 20px;
    border-bottom: 2px solid #ecf0f1;
}

.session-controls {
    display: flex;
    align-items: center;
    gap: 15px;
}

.score-display {
    background: #27ae60;
    color: white;
    padding: 8px 15px;
    border-radius: 20px;
    font-weight: bold;
}

.btn-primary,
.btn-secondary,
.btn-voice {
    padding: 12px 25px;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    font-size: 1em;
    transition: all 0.3s ease;
}

.btn-primary {
    background: #3498db;
    color: white;
}

.btn-primary:hover {
    background: #2980b9;
}

.btn-secondary {
    background: #e74c3c;
    color: white;
}

.btn-secondary:hover {
    background: #c0392b;
}

.btn-voice {
    background: #9b59b6;
    color: white;
}

.btn-voice:hover {
    background: #8e44ad;
}

.professor-message {
    display: flex;
    gap: 15px;
    margin-bottom: 20px;
    align-items: flex-start;
}

.avatar {
    font-size: 2em;
    flex-shrink: 0;
}

.message-content {
    flex: 1;
    background: #f8f9fa;
    padding: 20px;
    border-radius: 10px;
    border-left: 4px solid #3498db;
}

.voice-controls {
    margin: 20px 0;
    text-align: center;
}

.listening-indicator {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    background: #fff3cd;
    padding: 10px 20px;
    border-radius: 25px;
    border: 1px solid #ffeaa7;
}

.pulse {
    width: 12px;
    height: 12px;
    background: #e74c3c;
    border-radius: 50%;
    animation: pulse 1.5s infinite;
}

@keyframes pulse {
    0% {
        transform: scale(0.95);
        opacity: 0.7;
    }

    50% {
        transform: scale(1.1);
        opacity: 1;
    }

    100% {
        transform: scale(0.95);
        opacity: 0.7;
    }
}

.answer-section {
    margin: 30px 0;
}

.answer-section h3 {
    margin-bottom: 15px;
    color: #2c3e50;
}

#studentAnswer {
    width: 100%;
    height: 120px;
    padding: 15px;
    border: 2px solid #bdc3c7;
    border-radius: 8px;
    font-size: 1em;
    resize: vertical;
    font-family: inherit;
}

.answer-buttons {
    display: flex;
    gap: 15px;
    margin-top: 15px;
    flex-wrap: wrap;
}

.feedback-area {
    margin-top: 30px;
}

.score-badge {
    display: inline-block;
    background: #27ae60;
    color: white;
    padding: 8px 15px;
    border-radius: 15px;
    margin: 10px 0;
    font-weight: bold;
}

.progress-section {
    margin-top: 40px;
    padding-top: 20px;
    border-top: 2px solid #ecf0f1;
}

.progress-bar {
    width: 100%;
    height: 10px;
    background: #ecf0f1;
    border-radius: 5px;
    overflow: hidden;
    margin: 15px 0;
}

.progress-fill {
    height: 100%;
    background: #27ae60;
    transition: width 0.3s ease;
}

.history-container {
    max-height: 300px;
    overflow-y: auto;
    margin-top: 20px;
}

.history-item {
    background: #f8f9fa;
    padding: 15px;
    margin: 10px 0;
    border-radius: 8px;
    border-left: 4px solid #95a5a6;
}

/* Responsive design */
@media (max-width: 768px) {
    .container {
        margin: 10px;
        border-radius: 10px;
    }

    .topic-selection,
    .viva-session {
        padding: 20px;
    }

    .session-header {
        flex-direction: column;
        gap: 15px;
        align-items: flex-start;
    }

    .answer-buttons {
        flex-direction: column;
    }

    header h1 {
        font-size: 2em;
    }
}