:root {
            --primary: #4F46E5;
            --primary-hover: #4338CA;
            --background: #F9FAFB;
            --card-bg: #FFFFFF;
            --text-main: #111827;
            --text-muted: #4B5563;
            --border: #E5E7EB;
            --error: #EF4444;
            --success: #10B981;
            --pdf-color: #EF4444;
            --word-color: #2563EB;
            --pptx-color: #F59E0B;
            --image-color: #10B981;
        }

        * {
            box-sizing: border-box;
            margin: 0;
            padding: 0;
            font-family: 'Inter', sans-serif;
        }

        body {
            background-color: var(--background);
            color: var(--text-main);
            min-height: 100vh;
            display: flex;
            flex-direction: column;
            align-items: center;
            padding: 20px;
        }

        header {
            text-align: center;
            margin: 30px 0;
        }

        header h1 {
            font-size: 2.5rem;
            background: linear-gradient(90deg, #4F46E5, #7C3AED, #EC4899);
            -webkit-background-clip: text;
            background-clip: text;
            color: transparent;
            font-weight: 700;
            margin-bottom: 8px;
        }

        header p {
            color: var(--text-muted);
            font-size: 1.1rem;
        }

        /* Container Wrapper (single column — Monetag's real formats like
           Push/Vignette/IPP don't need dedicated fixed-size ad space) */
        .main-container {
            width: 100%;
            max-width: 800px;
            display: grid;
            grid-template-columns: 1fr;
            gap: 20px;
        }

        /* App Main Area */
        .app-card {
            background: var(--card-bg);
            border: 1px solid var(--border);
            border-radius: 16px;
            padding: 30px;
            box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.05);
            min-height: 450px;
            display: flex;
            flex-direction: column;
            justify-content: center;
            position: relative;
        }

        /* Tool Cards Grid Layout */
        .tools-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
            gap: 20px;
            width: 100%;
        }

        .tool-box {
            background: var(--card-bg);
            border: 1px solid var(--border);
            border-top: 4px solid var(--box-color, var(--primary));
            border-radius: 12px;
            padding: 24px;
            text-align: center;
            cursor: pointer;
            transition: all 0.2s ease;
        }

        .tool-box:hover {
            border-color: var(--box-color, var(--primary));
            border-top-color: var(--box-color, var(--primary));
            transform: translateY(-4px);
            box-shadow: 0 10px 15px -3px rgba(79, 70, 229, 0.15);
        }

        .tool-box .icon {
            font-size: 40px;
            color: var(--box-color, var(--primary));
            margin-bottom: 12px;
        }

        .tool-box[data-type="pdf"] { --box-color: var(--pdf-color); }
        .tool-box[data-type="word"] { --box-color: var(--word-color); }
        .tool-box[data-type="pptx"] { --box-color: var(--pptx-color); }
        .tool-box[data-type="image"] { --box-color: var(--image-color); }

        .tool-box h3 {
            font-size: 1.2rem;
            margin-bottom: 6px;
        }

        .tool-box p {
            font-size: 0.85rem;
            color: var(--text-muted);
        }

        .level-box {
            background: var(--card-bg);
            border: 2px solid var(--border);
            border-radius: 12px;
            padding: 20px;
            text-align: left;
            cursor: pointer;
            transition: all 0.2s ease;
            margin-bottom: 14px;
            display: flex;
            justify-content: space-between;
            align-items: center;
            gap: 10px;
        }

        .level-box:hover {
            border-color: var(--primary);
            transform: translateY(-2px);
        }

        .level-box h3 {
            font-size: 1.05rem;
            margin-bottom: 4px;
        }

        .level-box p {
            font-size: 0.82rem;
            color: var(--text-muted);
        }

        .level-tag {
            font-size: 0.75rem;
            font-weight: 700;
            padding: 4px 10px;
            border-radius: 20px;
            color: #fff;
            white-space: nowrap;
        }
        .workspace-view {
            display: none;
            text-align: center;
            width: 100%;
        }

        .back-btn {
            background: none;
            border: none;
            color: var(--primary);
            font-weight: 600;
            display: inline-flex;
            align-items: center;
            gap: 5px;
            cursor: pointer;
            margin-bottom: 20px;
            align-self: flex-start;
        }

        /* Drag & Drop Upload Zone */
        .upload-zone {
            border: 3px dashed var(--border);
            border-radius: 12px;
            padding: 50px 20px;
            cursor: pointer;
            transition: border-color 0.2s;
            background: #FAFAFA;
        }

        .upload-zone:hover {
            border-color: var(--primary);
        }

        .upload-zone .icon {
            font-size: 48px;
            color: var(--text-muted);
            margin-bottom: 10px;
        }

        /* Processing/Loading UI */
        .processing-box {
            display: none;
            text-align: center;
        }

        .progress-bar-container {
            width: 100%;
            height: 8px;
            background: var(--border);
            border-radius: 4px;
            margin: 20px 0;
            overflow: hidden;
        }

        .progress-bar {
            width: 0%;
            height: 100%;
            background: var(--primary);
            transition: width 0.1s linear;
        }

        .status-text {
            font-weight: 500;
            color: var(--text-muted);
        }

        /* Download View */
        .download-box {
            display: none;
            text-align: center;
        }

        .stats-badge {
            background: rgba(16, 185, 129, 0.1);
            color: var(--success);
            padding: 8px 16px;
            border-radius: 20px;
            display: inline-block;
            font-weight: 600;
            margin-bottom: 15px;
        }

        .download-btn {
            background: var(--success);
            color: white;
            border: none;
            padding: 14px 32px;
            font-size: 1.1rem;
            font-weight: 600;
            border-radius: 8px;
            cursor: pointer;
            box-shadow: 0 4px 6px rgba(16, 185, 129, 0.2);
        }

        /* Sliding Error Custom Pop-up Toast */
        .error-toast {
            position: fixed;
            top: -100px;
            left: 50%;
            transform: translateX(-50%);
            background: #FEF2F2;
            border: 1px solid #FCA5A5;
            border-radius: 8px;
            padding: 16px 24px;
            display: flex;
            align-items: center;
            gap: 12px;
            box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
            transition: top 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
            z-index: 1000;
            width: 90%;
            max-width: 500px;
        }

        .error-toast.show {
            top: 24px;
        }

        .error-toast .toast-icon {
            color: var(--error);
            font-size: 24px;
        }

        .error-toast .toast-msg {
            color: #991B1B;
            font-size: 0.9rem;
            font-weight: 500;
            line-height: 1.4;
        }

        /* Mandatory Video Ad Interstitial Lock Screen */
        .video-lock-overlay {
            position: fixed;
            top: 0; left: 0; width: 100%; height: 100%;
            background: rgba(0,0,0,0.9);
            z-index: 9999;
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
            color: white;
            padding: 20px;
            display: none;
        }

        .video-player-mock {
            width: 100%;
            max-width: 640px;
            aspect-ratio: 16/9;
            background: #111;
            border: 2px solid #333;
            border-radius: 8px;
            display: flex;
            align-items: center;
            justify-content: center;
            position: relative;
            margin-bottom: 20px;
        }

        .video-timer {
            position: absolute;
            top: 15px; right: 15px;
            background: rgba(0,0,0,0.7);
            padding: 6px 12px;
            border-radius: 4px;
            font-size: 0.85rem;
            font-weight: bold;
        }