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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background-color: #f8fafc;
    color: #334155;
    line-height: 1.6;
}

.container {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header */
.header {
    background: white;
    border-bottom: 1px solid #e2e8f0;
    padding: 1rem 2rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1);
}

.back-btn {
    background: none;
    border: none;
    color: #6366f1;
    font-size: 0.9rem;
    cursor: pointer;
    padding: 0.5rem 1rem;
    border-radius: 0.5rem;
    transition: background-color 0.2s;
}

.back-btn:hover {
    background-color: #f1f5f9;
}

.title {
    font-size: 1.5rem;
    font-weight: 600;
    color: #1e293b;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

/* Main Content */
.main-content {
    flex: 1;
    display: grid;
    grid-template-columns: 400px 1fr;
    gap: 2rem;
    padding: 2rem;
    max-width: 1400px;
    margin: 0 auto;
    width: 100%;
}

/* Config Panel */
.config-panel {
    background: white;
    border-radius: 1rem;
    padding: 2rem;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    height: fit-content;
}

.config-panel h2 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
    color: #1e293b;
}

.form-group {
    margin-bottom: 1.5rem;
}

.form-group label {
    display: block;
    font-weight: 500;
    margin-bottom: 0.5rem;
    color: #374151;
    font-size: 0.9rem;
}

.form-select {
    width: 100%;
    padding: 0.75rem 1rem;
    border: 1px solid #d1d5db;
    border-radius: 0.5rem;
    font-size: 0.9rem;
    background: white;
    color: #374151;
    transition: border-color 0.2s, box-shadow 0.2s;
}

.form-select:focus {
    outline: none;
    border-color: #6366f1;
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

.form-select:disabled {
    background-color: #f9fafb;
    color: #9ca3af;
    cursor: not-allowed;
}

.generate-btn {
    width: 100%;
    background: linear-gradient(135deg, #6366f1 0%, #8b5cf6 100%);
    color: white;
    border: none;
    padding: 1rem 1.5rem;
    border-radius: 0.75rem;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: transform 0.2s, box-shadow 0.2s;
    margin-bottom: 1.5rem;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

.generate-btn:hover:not(:disabled) {
    transform: translateY(-1px);
    box-shadow: 0 10px 25px -5px rgba(99, 102, 241, 0.4);
}

.generate-btn:disabled {
    background: #e5e7eb;
    color: #9ca3af;
    cursor: not-allowed;
    transform: none;
    box-shadow: none;
}

.note {
    background: #fef3c7;
    border: 1px solid #fbbf24;
    border-radius: 0.5rem;
    padding: 1rem;
    font-size: 0.85rem;
    color: #92400e;
}

.note p {
    margin: 0;
}

/* Preview Panel */
.preview-panel {
    background: white;
    border-radius: 1rem;
    padding: 2rem;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
}

.preview-panel h2 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
    color: #1e293b;
}

.preview-content {
    min-height: 500px;
    border: 2px dashed #e2e8f0;
    border-radius: 0.75rem;
    display: flex;
    align-items: center;
    justify-content: center;
    background: #f8fafc;
}

.preview-placeholder {
    text-align: center;
    color: #64748b;
}

.book-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
    opacity: 0.7;
}

.preview-placeholder p {
    font-size: 1.1rem;
    margin-bottom: 0.5rem;
    font-weight: 500;
}

.preview-placeholder small {
    font-size: 0.9rem;
    color: #94a3b8;
}

/* Generated Content Styles */
.lesson-plan {
    text-align: left;
    padding: 2rem;
    background: white;
    border-radius: 0.5rem;
    border: 1px solid #e2e8f0;
}

.lesson-plan h3 {
    color: #1e293b;
    margin-bottom: 1rem;
    font-size: 1.2rem;
}

.lesson-plan h4 {
    color: #374151;
    margin: 1.5rem 0 0.75rem 0;
    font-size: 1rem;
}

.lesson-plan ul {
    margin-left: 1.5rem;
    margin-bottom: 1rem;
}

.lesson-plan li {
    margin-bottom: 0.5rem;
    color: #4b5563;
}

.lesson-info {
    background: #f1f5f9;
    padding: 1rem;
    border-radius: 0.5rem;
    margin-bottom: 1.5rem;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 1rem;
}

.info-item {
    text-align: center;
}

.info-label {
    font-size: 0.8rem;
    color: #64748b;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 0.25rem;
}

.info-value {
    font-weight: 600;
    color: #1e293b;
}

/* Lesson Plan Display */
.lesson-plan {
    background: white;
    border-radius: 0.5rem;
    padding: 2rem;
    box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1);
}

.brief-lesson {
    max-width: 1000px;
    margin: 0 auto;
}

.lesson-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
    border-bottom: 2px solid #e2e8f0;
    padding-bottom: 1rem;
}

.lesson-header h2 {
    font-size: 1.875rem;
    font-weight: 700;
    color: #1e293b;
}

.badge {
    background: #dbeafe;
    color: #1e40af;
    padding: 0.5rem 1rem;
    border-radius: 9999px;
    font-size: 0.875rem;
    font-weight: 500;
}

/* Phase Cards */
.phase-card {
    background: #f8fafc;
    border: 1px solid #e2e8f0;
    border-radius: 0.5rem;
    padding: 1.5rem;
    margin-bottom: 1rem;
    transition: box-shadow 0.2s;
}

.phase-card:hover {
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
}

.phase-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
}

.phase-header h4 {
    font-size: 1.125rem;
    font-weight: 600;
    color: #1e293b;
    margin: 0;
}

.phase-summary {
    color: #64748b;
    font-size: 0.9375rem;
    line-height: 1.6;
    margin: 0;
}

.expand-btn {
    background: linear-gradient(135deg, #6366f1 0%, #4f46e5 100%);
    color: white;
    border: none;
    padding: 0.625rem 1.25rem;
    border-radius: 0.5rem;
    font-size: 0.875rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
    box-shadow: 0 2px 4px rgba(99, 102, 241, 0.2);
}

.expand-btn:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(99, 102, 241, 0.3);
}

.expand-btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

.expanded-content {
    margin-top: 1rem;
    padding-top: 1rem;
    border-top: 1px solid #e2e8f0;
}

.expanded-section-content {
    background: white;
    padding: 1.25rem;
    border-radius: 0.5rem;
    border-left: 4px solid #6366f1;
}

.expanded-section-content h4 {
    font-size: 1rem;
    font-weight: 600;
    color: #1e293b;
    margin: 1.25rem 0 0.75rem 0;
}

.expanded-section-content h4:first-child {
    margin-top: 0;
}

.expanded-section-content p {
    color: #475569;
    line-height: 1.7;
    margin-bottom: 1rem;
}

.expanded-section-content ol,
.expanded-section-content ul {
    margin-left: 1.5rem;
    color: #475569;
}

.expanded-section-content li {
    margin-bottom: 0.5rem;
    line-height: 1.6;
}

.teacher-notes {
    background: #fef3c7;
    border-left: 4px solid #f59e0b;
    padding: 1rem;
    border-radius: 0.375rem;
    margin-top: 1rem;
    font-size: 0.9375rem;
    color: #78350f;
}

/* Responsive Design */
@media (max-width: 1024px) {
    .main-content {
        grid-template-columns: 1fr;
        gap: 1.5rem;
        padding: 1rem;
    }
    
    .config-panel {
        order: 1;
    }
    
    .preview-panel {
        order: 2;
    }
}

@media (max-width: 768px) {
    .header {
        padding: 1rem;
        flex-direction: column;
        gap: 1rem;
    }
    
    .title {
        font-size: 1.25rem;
    }
    
    .config-panel,
    .preview-panel {
        padding: 1.5rem;
    }
    
    .main-content {
        padding: 1rem;
    }
}

/* Loading Animation */
.loading {
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 3px solid rgba(255, 255, 255, 0.3);
    border-radius: 50%;
    border-top-color: white;
    animation: spin 1s ease-in-out infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

.loading {
    display: inline-block;
    width: 16px;
    height: 16px;
    border: 2px solid rgba(255, 255, 255, 0.3);
    border-radius: 50%;
    border-top-color: white;
    animation: spin 0.6s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* Lesson images */
.lesson-image {
    max-width: 100%;
    height: auto;
    margin: 1rem 0;
    border-radius: 0.5rem;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}