/* Reset & Base Styles */
        *, *::before, *::after {
            box-sizing: border-box;
            margin: 0;
            padding: 0;
        }

        html {
            line-height: 1.15;
            -webkit-text-size-adjust: 100%;
            scroll-behavior: smooth;
        }

        body {
            font-family: 'Inter', 'Roboto', -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Oxygen', 'Ubuntu', 'Cantarell', sans-serif;
            line-height: 1.6;
            color: #1F2937;
            background-color: #FFFFFF;
            -webkit-font-smoothing: antialiased;
            -moz-osx-font-smoothing: grayscale;
        }

        /* Color Variables */
        :root {
            --primary-blue: #2563EB;
            --primary-blue-hover: #1D4ED8;
            --primary-blue-light: #EBF4FF;
            --primary-red: #D32F2F;
            --text-primary: #1F2937;
            --text-secondary: #6B7280;
            --text-light: #9CA3AF;
            --text-white: #FFFFFF;
            --text-error: #DC2626;
            --background-primary: #FFFFFF;
            --background-secondary: #F5F8FE;
            --border-light: #E5E7EB;
            --border-focus: #2563EB;
            --shadow-light: rgba(0, 0, 0, 0.1);
            --spacing-xs: 0.5rem;
            --spacing-sm: 1rem;
            --spacing-md: 1.5rem;
            --spacing-lg: 2rem;
            --spacing-xl: 3rem;
            --spacing-xxl: 4rem;
            --radius-sm: 4px;
            --radius-md: 8px;
            --radius-lg: 12px;
            --radius-xl: 16px;
            --transition-fast: 0.2s ease;
            --transition-medium: 0.3s ease;
        }

        .sr-only {
            position: absolute;
            width: 1px;
            height: 1px;
            padding: 0;
            margin: -1px;
            overflow: hidden;
            clip: rect(0, 0, 0, 0);
            white-space: nowrap;
            border: 0;
        }

        .container {
            width: 100%;
            max-width: 800px;
            margin: 0 auto;
            padding: 0 var(--spacing-md);
        }

        /* Header Styles */
        .header {
            background-color: var(--background-primary);
            border-bottom: 1px solid var(--border-light);
            padding: var(--spacing-md) 0;
            position: sticky;
            top: 0;
            z-index: 100;
            box-shadow: 0 1px 3px rgba(0, 0, 0, 0.05);
        }

        .header-content {
            display: flex;
            align-items: center;
            justify-content: space-between;
        }

        .back-link {
            display: flex;
            align-items: center;
            gap: var(--spacing-xs);
            color: var(--primary-blue);
            font-weight: 500;
            transition: color var(--transition-fast);
            padding: var(--spacing-xs) 0;
            text-decoration: none;
        }

        .back-link:hover {
            color: var(--primary-blue-hover);
        }

        .back-link svg {
            width: 16px;
            height: 16px;
        }

        .header-brand {
            display: flex;
            flex-direction: column;
            align-items: flex-end;
            text-align: right;
        }

        .brand-title {
            font-size: 1.5rem;
            font-weight: 700;
            color: var(--primary-red);
            margin-bottom: 0;
            line-height: 1;
        }

        .brand-subtitle {
            font-size: 0.75rem;
            color: var(--text-light);
            margin-bottom: 0;
            line-height: 1;
        }

        /* Main Content */
        .main-content {
            background-color: var(--background-secondary);
            min-height: calc(100vh - 80px);
            padding: var(--spacing-xxl) 0;
        }

        .page-header {
            text-align: center;
            margin-bottom: var(--spacing-xxl);
        }

        .page-title {
            font-size: 2.5rem;
            font-weight: 700;
            color: var(--text-primary);
            margin-bottom: var(--spacing-md);
        }

        .page-subtitle {
            font-size: 1.125rem;
            color: var(--text-secondary);
            max-width: 600px;
            margin: 0 auto;
            line-height: 1.6;
        }

        /* Form Styles */
        .analysis-form {
            background-color: var(--background-primary);
            border-radius: var(--radius-xl);
            padding: var(--spacing-xl);
            box-shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
            border: 1px solid var(--border-light);
        }

        .form-step {
            margin-bottom: var(--spacing-xl);
        }

        .form-step:last-child {
            margin-bottom: 0;
        }

        .step-label {
            display: block;
            font-weight: 600;
            color: var(--text-primary);
            margin-bottom: var(--spacing-sm);
            font-size: 1.125rem;
        }

        .required::after {
            content: '*';
            color: var(--text-error);
            margin-left: 4px;
        }

        .form-select, .form-input {
            width: 100%;
            padding: var(--spacing-sm) var(--spacing-md);
            border: 2px solid var(--border-light);
            border-radius: var(--radius-md);
            background-color: var(--background-primary);
            color: var(--text-primary);
            transition: all var(--transition-fast);
            font-size: 1rem;
        }

        .form-select:focus, .form-input:focus {
            outline: none;
            border-color: var(--border-focus);
            box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
        }

        .form-textarea {
            width: 100%;
            min-height: 120px;
            padding: var(--spacing-sm) var(--spacing-md);
            border: 2px solid var(--border-light);
            border-radius: var(--radius-md);
            background-color: var(--background-primary);
            color: var(--text-primary);
            transition: all var(--transition-fast);
            font-size: 1rem;
            resize: vertical;
            font-family: inherit;
        }

        .form-textarea:focus {
            outline: none;
            border-color: var(--border-focus);
            box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
        }

        .word-count {
            font-size: 0.875rem;
            color: var(--text-light);
            text-align: right;
            margin-top: var(--spacing-xs);
        }

        .word-count.warning {
            color: #F59E0B;
        }

        .word-count.error {
            color: var(--text-error);
        }

        .field-description {
            font-size: 0.875rem;
            color: var(--text-secondary);
            margin-top: var(--spacing-xs);
        }

        .field-group {
            margin-bottom: var(--spacing-lg);
        }

        .field-group:last-child {
            margin-bottom: 0;
        }

        /* try to fix the bugs */
        .upload-area {
            border: 2px dashed var(--border-light);
            border-radius: var(--radius-md);
            padding: var(--spacing-xl);
            text-align: center;
            background-color: var(--background-secondary);
            transition: all var(--transition-fast);
            cursor: pointer;
            position: relative;
        }
        
        .upload-area:hover,
        .upload-area.dragover {
            border-color: var(--primary-blue);
            background-color: var(--primary-blue-light);
        }

        .upload-icon {
            width: 48px;
            height: 48px;
            margin: 0 auto var(--spacing-md);
            color: var(--text-light);
        }

        .upload-text {
            color: var(--text-secondary);
            margin-bottom: var(--spacing-sm);
        }

        .upload-text strong {
            color: var(--primary-blue);
        }

        .upload-requirements {
            font-size: 0.875rem;
            color: var(--text-light);
        }

        .file-input {
            position: absolute;
            opacity: 0;
            pointer-events: none;
        }

        .uploaded-file {
            display: flex;
            align-items: center;
            justify-content: space-between;
            padding: var(--spacing-sm);
            background-color: var(--primary-blue-light);
            border-radius: var(--radius-md);
            margin-top: var(--spacing-sm);
        }

        .file-info {
            display: flex;
            align-items: center;
            gap: var(--spacing-xs);
        }

        .file-name {
            font-weight: 500;
            color: var(--text-primary);
        }

        .file-size {
            color: var(--text-secondary);
            font-size: 0.875rem;
        }

        .remove-file {
            background: none;
            border: none;
            color: var(--text-error);
            cursor: pointer;
            padding: var(--spacing-xs);
            border-radius: var(--radius-sm);
            transition: background-color var(--transition-fast);
        }

        .remove-file:hover {
            background-color: rgba(220, 38, 38, 0.1);
        }

        /* update: fix click error: allow internal label as click face */
        .upload-click-surface {
            display: flex;              
            flex-direction: column;
            align-items: center;
            text-align: center;
            gap: 0.5rem;
            cursor: pointer;           
            color: inherit;            
            text-decoration: none;      
        }
        
        /* update: fix click error: all area can click input */
        .upload-click-surface * {
            pointer-events: none;
        }
        

        

        /* Button Styles */
        .analyze-button {
            width: auto;
            padding: var(--spacing-md) var(--spacing-xl);
            background: linear-gradient(135deg, var(--primary-blue), #3B82F6);
            color: var(--text-white);
            border: none;
            border-radius: var(--radius-md);
            font-size: 1.125rem;
            font-weight: 600;
            cursor: pointer;
            transition: all var(--transition-fast);
            margin-top: var(--spacing-xl);
            box-shadow: 0 4px 12px rgba(37, 99, 235, 0.2);
            display: block;
            margin-left: auto;
            margin-right: auto;
        }

        .analyze-button:hover:not(:disabled) {
            background: linear-gradient(135deg, var(--primary-blue-hover), #2563EB);
            transform: translateY(-2px);
            box-shadow: 0 6px 16px rgba(37, 99, 235, 0.3);
        }

        .analyze-button:disabled {
            background: var(--text-light);
            cursor: not-allowed;
            transform: none;
            box-shadow: none;
        }

        .error-message {
            color: var(--text-error);
            font-size: 0.875rem;
            margin-top: var(--spacing-sm);
            text-align: center;
            opacity: 0;
            transition: opacity var(--transition-fast);
        }

        .error-message.show {
            opacity: 1;
        }

        /* Conditional Fields */
        .conditional-fields {
            margin-top: var(--spacing-lg);
            opacity: 0;
            max-height: 0;
            overflow: hidden;
            transition: all var(--transition-medium);
        }

        .conditional-fields.show {
            opacity: 1;
            max-height: 2000px;
        }

        .field-content {
            display: none;
        }

        .field-content.active {
            display: block;
            animation: fadeIn 0.4s ease-out;
        }

        @keyframes fadeIn {
            from {
                opacity: 0;
                transform: translateY(10px);
            }
            to {
                opacity: 1;
                transform: translateY(0);
            }
        }

        /* Responsive */
        @media (max-width: 768px) {
            .container {
                padding: 0 var(--spacing-sm);
            }
            
            .page-title {
                font-size: 2rem;
            }
            
            .page-subtitle {
                font-size: 1rem;
            }
            
            .analysis-form {
                padding: var(--spacing-lg);
            }
            
            .header-content {
                gap: var(--spacing-sm);
            }
            
            .brand-title {
                font-size: 1.25rem;
            }
            
            .upload-area {
                padding: var(--spacing-lg);
            }
        }

        :focus {
            outline: 2px solid var(--primary-blue);
            outline-offset: 2px;
        }

        :focus:not(:focus-visible) {
            outline: none;
        }