:root {
            --primary-blue: #1a365d;
            --secondary-blue: #2c5282;
            --accent-blue: #4299e1;
            --light-blue: #bee3f8;
            --medical-teal: #38b2ac;
            --medical-green: #48bb78;
            --medical-red: #f56565;
            --medical-purple: #9f7aea;
            --bg-light: #f7fafc;
            --card-bg: #ffffff;
            --text-dark: #2d3748;
            --text-light: #718096;
            --border-color: #e2e8f0;
        }
        * {
            box-sizing: border-box;
        }
        body {
            margin: 0;
            font-family: 'Segoe UI', 'Roboto', 'Helvetica Neue', Arial, sans-serif;
            background: linear-gradient(135deg, #f5f7fa 0%, #e4e8f0 100%);
            color: var(--text-dark);
            line-height: 1.6;
        }
        header {
            background: linear-gradient(135deg, var(--primary-blue) 0%, var(--secondary-blue) 100%);
            color: white;
            padding: 20px 30px;
            text-align: center;
            box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
            position: relative;
            overflow: hidden;
        }
        header::before {
            content: "";
            position: absolute;
            top: 0;
            left: 0;
            right: 0;
            bottom: 0;
            background: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" preserveAspectRatio="none" opacity="0.05"><path d="M50,10 L60,30 L80,35 L65,50 L70,70 L50,60 L30,70 L35,50 L20,35 L40,30 Z" fill="white"/></svg>');
            background-size: 120px;
        }
        .header-content {
            display: flex;
            align-items: center;
            justify-content: center;
            gap: 20px;
            position: relative;
            z-index: 1;
        }
        .header-icon {
            font-size: 36px;
            color: var(--light-blue);
            animation: pulse 3s infinite;
        }
        @keyframes pulse {
            0%, 100% { opacity: 0.8; }
            50% { opacity: 1; }
        }
        .header-text h1 {
            margin: 0;
            font-size: 28px;
            font-weight: 700;
            letter-spacing: 0.5px;
        }
        .header-text p {
            margin: 8px 0 0;
            font-size: 16px;
            opacity: 0.9;
            font-weight: 300;
        }
        .container {
            max-width: 1200px;
            margin: 30px auto;
            padding: 0 20px;
        }
        .layout {
            display: flex;
            gap: 25px;
            align-items: flex-start;
        }
        .sidebar {
            width: 350px;
            flex-shrink: 0;
        }
        .panel {
            background: var(--card-bg);
            border-radius: 12px;
            padding: 22px;
            margin-bottom: 25px;
            box-shadow: 0 5px 15px rgba(0, 0, 0, 0.05);
            border: 1px solid var(--border-color);
            transition: transform 0.3s ease, box-shadow 0.3s ease;
        }
        .panel:hover {
            transform: translateY(-3px);
            box-shadow: 0 8px 20px rgba(0, 0, 0, 0.08);
        }
        .section-title {
            font-size: 20px;
            font-weight: 600;
            border-bottom: 3px solid var(--medical-teal);
            padding-bottom: 10px;
            margin-bottom: 18px;
            color: var(--primary-blue);
            display: flex;
            align-items: center;
            gap: 10px;
        }
        .section-title i {
            color: var(--accent-blue);
        }
        .biomarker-list {
            max-height: 350px;
            overflow-y: auto;
            padding-right: 8px;
        }
        .biomarker-list::-webkit-scrollbar {
            width: 8px;
        }
        .biomarker-list::-webkit-scrollbar-track {
            background: #f1f1f1;
            border-radius: 4px;
        }
        .biomarker-list::-webkit-scrollbar-thumb {
            background: var(--accent-blue);
            border-radius: 4px;
        }
        .biomarker-item {
            padding: 14px 16px;
            margin-bottom: 10px;
            background: #f8fafc;
            border-left: 5px solid var(--accent-blue);
            border-radius: 8px;
            cursor: pointer;
            transition: all 0.2s ease;
            display: flex;
            align-items: center;
            gap: 12px;
            border: 1px solid var(--border-color);
        }
        .biomarker-item:hover {
            background: #edf2f7;
            transform: translateX(5px);
            box-shadow: 0 3px 8px rgba(66, 153, 225, 0.1);
        }
        .biomarker-item.selected {
            background: linear-gradient(135deg, #e6fffa 0%, #f0fff4 100%);
            border-left-color: var(--medical-green);
            border: 1px solid var(--medical-green);
            box-shadow: 0 3px 10px rgba(72, 187, 120, 0.15);
        }
        .biomarker-item i {
            color: var(--secondary-blue);
            font-size: 16px;
        }
        .biomarker-item.selected i {
            color: var(--medical-green);
        }
        .btn {
            padding: 14px 20px;
            border: none;
            border-radius: 8px;
            font-weight: 600;
            font-size: 15px;
            cursor: pointer;
            margin-top: 12px;
            transition: all 0.3s ease;
            display: flex;
            align-items: center;
            justify-content: center;
            gap: 10px;
            width: 100%;
            letter-spacing: 0.3px;
        }
        .btn:hover {
            transform: translateY(-2px);
            box-shadow: 0 5px 12px rgba(0, 0, 0, 0.15);
        }
        .btn:active {
            transform: translateY(0);
        }
        .btn.primary {
            background: linear-gradient(135deg, var(--accent-blue) 0%, var(--secondary-blue) 100%);
            color: white;
        }
        .btn.secondary {
            background: linear-gradient(135deg, #718096 0%, #4a5568 100%);
            color: white;
        }
        .btn.success {
            background: linear-gradient(135deg, var(--medical-green) 0%, #38a169 100%);
            color: white;
        }
        .btn:disabled {
            background: #cbd5e0;
            cursor: not-allowed;
            transform: none;
            box-shadow: none;
        }
        .view {
            display: none;
        }
        .view.active {
            display: block;
            animation: fadeIn 0.5s ease;
        }
        @keyframes fadeIn {
            from { opacity: 0; transform: translateY(10px); }
            to { opacity: 1; transform: translateY(0); }
        }
        .stats-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
            gap: 20px;
            margin-top: 20px;
        }
        .stat-card {
            background: white;
            padding: 20px;
            border-radius: 10px;
            text-align: center;
            border-top: 5px solid var(--accent-blue);
            box-shadow: 0 3px 10px rgba(0, 0, 0, 0.05);
            transition: all 0.3s ease;
        }
        .stat-card:hover {
            transform: translateY(-5px);
            box-shadow: 0 8px 15px rgba(0, 0, 0, 0.08);
        }
        .stat-card:nth-child(2) { border-top-color: var(--medical-teal); }
        .stat-card:nth-child(3) { border-top-color: var(--medical-green); }
        .stat-card:nth-child(4) { border-top-color: var(--medical-purple); }
        .stat-card:nth-child(5) { border-top-color: var(--medical-red); }
        .stat-card:nth-child(6) { border-top-color: #ed8936; }
        .stat-card:nth-child(7) { border-top-color: #9f7aea; }
        .stat-card:nth-child(8) { border-top-color: #f56565; }
        .stat-card:nth-child(9) { border-top-color: #38a169; }
        .stat-card:nth-child(10) { border-top-color: #0bc5ea; }
        .stat-card:nth-child(11) { border-top-color: #d53f8c; }
        .stat-card strong {
            display: block;
            font-size: 24px;
            margin-top: 10px;
            color: var(--primary-blue);
        }
        .chart-container {
            background: white;
            border-radius: 10px;
            padding: 25px;
            margin-top: 25px;
            box-shadow: 0 5px 15px rgba(0, 0, 0, 0.05);
            border: 1px solid var(--border-color);
        }
        canvas {
            max-height: 350px;
            width: 100% !important;
        }
        .file-upload {
            position: relative;
            padding: 25px;
            border: 2px dashed var(--accent-blue);
            border-radius: 10px;
            text-align: center;
            background: #f0f9ff;
            margin-bottom: 20px;
            transition: all 0.3s ease;
        }
        .file-upload:hover {
            background: #e6f7ff;
            border-color: var(--secondary-blue);
        }
        .file-upload input {
            position: absolute;
            width: 100%;
            height: 100%;
            top: 0;
            left: 0;
            opacity: 0;
            cursor: pointer;
        }
        .file-upload i {
            font-size: 40px;
            color: var(--accent-blue);
            margin-bottom: 15px;
        }
        .file-upload p {
            margin: 0;
            font-weight: 500;
            color: var(--secondary-blue);
        }
        .status-box {
            background: #f8fafc;
            padding: 15px;
            border-radius: 8px;
            border-left: 5px solid var(--medical-green);
            font-weight: 500;
            margin-top: 15px;
        }
        .status-box.loading {
            border-left-color: var(--accent-blue);
        }
        .status-box.error {
            border-left-color: var(--medical-red);
        }
        .action-buttons {
            display: flex;
            gap: 15px;
            margin-top: 15px;
        }
        .action-buttons .btn {
            flex: 1;
            margin-top: 0;
        }
        .back-button {
            display: inline-flex;
            align-items: center;
            gap: 8px;
            color: var(--secondary-blue);
            background: #edf2f7;
            padding: 12px 20px;
            border-radius: 8px;
            text-decoration: none;
            font-weight: 500;
            transition: all 0.3s ease;
        }
        .back-button:hover {
            background: #e2e8f0;
            transform: translateX(-3px);
        }
        @media (max-width: 900px) {
            .layout {
                flex-direction: column;
            }
            .sidebar {
                width: 100%;
            }
            .header-content {
                flex-direction: column;
                gap: 10px;
            }
            .stats-grid {
                grid-template-columns: repeat(2, 1fr);
            }
        }
        @media (max-width: 600px) {
            .stats-grid {
                grid-template-columns: 1fr;
            }
            .header-text h1 {
                font-size: 22px;
            }
        }
    </style>
    
</head>
<body>
    <header>
        <div class="header-content">
            <div class="header-icon">
                <i class="fas fa-dna"></i>
            </div>
            <div class="header-text">
                <h1>BioStat</h1>
                <p class="subtitle">Disease Analyzer</p>
                <p>Advanced CSV-based statistical analysis tool for medical research</p>
            </div>
        </div>
    <header>
    <div class="header-content">
        <div class="header-icon">
            <i class="fas fa-dna"></i>
        </div>
        <div class="header-text">
            <h1>BioStat</h1>
            <p class="subtitle">Disease Biomarker Analyzer</p>
            <p>Advanced CSV-based statistical analysis tool for medical research</p>
        </div>
    </div>
</header>

<!-- Main Content -->
<div style="flex:1">

    <!-- Welcome View -->
    <div id="welcomeView" class="panel view active">
        <h2 class="section-title">
            <i class="fas fa-heartbeat"></i>
            Welcome to BioStat
        </h2>

        <p>
            BioStat enables researchers to explore biomarker datasets of diseases
            through patient-level statistics, interactive visualizations, and exportable results.
        </p>

        <ol>
            <li>
                <strong>Upload your CSV dataset</strong> using the panel on the left
            </li>
            <li>
                <strong>Select a biomarker</strong> to examine its statistical profile
            </li>
            <li>
                <strong>Analyze distributions</strong> and export findings for research use
            </li>
        </ol>

        <!-- Decorative feature cards -->
        <div class="stats-grid welcome-features">

            <div class="stat-card feature-card">
                <i class="fas fa-users"></i>
                <strong>Patient Analysis</strong>
            </div>

            <div class="stat-card feature-card">
                <i class="fas fa-chart-line"></i>
                <strong>Statistical Charts</strong>
            </div>

            <div class="stat-card feature-card">
                <i class="fas fa-file-export"></i>
                <strong>Export Results</strong>
                
            </div>

        </div>
    </div>

</div>