:root {
            --bg-base: #f0f4f8;
            --container-bg: #ffffff;
            --text-main: #2c3e50;
            --abacus-wood: #8e44ad;
            --abacus-beam: #34495e;
            --bead-color: #f1c40f;
            --bead-active: #e67e22;
            --accent-blue: #3498db;
            --accent-green: #2ecc71;
            --parent-panel: #ffeaa7;
        }

        * {
            box-sizing: border-box;
            margin: 0;
            padding: 0;
            font-family: 'Comic Sans MS', 'Chalkboard SE', sans-serif;
        }

        body {
            background-color: var(--bg-base);
            color: var(--text-main);
            display: flex;
            justify-content: center;
            align-items: center;
            min-height: 100vh;
            padding: 80px 20px 20px 20px;;
        }

        .lab-window {
            background: var(--container-bg);
            border-radius: 24px;
            box-shadow: 0 15px 40px rgba(0,0,0,0.08);
            width: 100%;
            max-width: 980px;
            padding: 25px;
            border: 5px solid #dcdde1;
        }

        /* Layout Framework */
        .grid-core {
            display: grid;
            grid-template-columns: 1fr 340px;
            gap: 25px;
            margin-top: 20px;
        }

        @media (max-width: 820px) {
            .grid-core { grid-template-columns: 1fr; }
        }

        /* Top Bar Layout */
        .lab-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            padding-bottom: 15px;
            border-bottom: 3px dashed #f1f2f6;
        }

        .badge {
            padding: 8px 16px;
            border-radius: 12px;
            font-weight: bold;
            font-size: 1.1rem;
        }
        .score-badge { background-color: #fdcb6e; color: #2c3e50; }
        .greeting-banner { font-size: 1.5rem; font-weight: bold; color: var(--accent-blue); }

        /* Left Column: Virtual Abacus Canvas */
        .abacus-stage {
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
            background: #fafafa;
            border-radius: 16px;
            padding: 20px;
            border: 2px solid #e1b12c;
        }

        .abacus-counter-display {
            font-size: 1.8rem;
            font-weight: bold;
            color: #7f8c8d;
            margin-bottom: 10px;
            background: #fff;
            padding: 5px 20px;
            border-radius: 30px;
            border: 2px solid #edf2f7;
        }

        /* Physical Soroban CSS Render Frame */
        .abacus-frame {
            width: 100%;
            max-width: 460px;
            background-color: #5e35b1;
            border: 14px solid var(--abacus-wood);
            border-radius: 12px;
            padding: 0;
            position: relative;
            box-shadow: 0 8px 16px rgba(0,0,0,0.2);
        }

        /* Center Separator Beam Line */
        .abacus-beam {
            height: 14px;
            background-color: var(--abacus-beam);
            width: 100%;
            position: absolute;
            top: 70px;
            left: 0;
            z-index: 5;
            box-shadow: 0 2px 4px rgba(0,0,0,0.3);
        }

        .abacus-rods-layer {
            display: flex;
            justify-content: space-around;
            height: 310px;
            position: relative;
            padding: 0 10px;
        }

        .rod {
            width: 6px;
            background: linear-gradient(to right, #bdc3c7, #95a5a6, #bdc3c7);
            height: 100%;
            position: relative;
        }

        /* Universal Bead Styles */
        .bead {
            position: absolute;
            width: 54px;
            height: 24px;
            background: radial-gradient(ellipse at center, #f39c12 0%, #d35400 100%);
            border-radius: 50% / 12px;
            left: -24px;
            cursor: pointer;
            box-shadow: 0 3px 5px rgba(0,0,0,0.2);
            transition: transform 0.2s cubic-bezier(0.25, 1, 0.5, 1);
            border: 1px solid #e67e22;
        }

        /* Top Deck: 5 Value Beading Coordinates */
        .bead.top-deck { top: 5px; }
        .bead.top-deck.active { transform: translateY(40px); background: radial-gradient(ellipse at center, #34e7e4 0%, #00d2d3 100%); border-color: #00d2d3; }

        /* Bottom Deck: 1 Value Beading Coordinates */
        .bead.bottom-deck.b1 { top: 96px; }
        .bead.bottom-deck.b2 { top: 124px; }
        .bead.bottom-deck.b3 { top: 152px; }
        .bead.bottom-deck.b4 { top: 180px; }

        /* Active Transformations relative to stacking orders */
        .bead.bottom-deck.b1.active { transform: translateY(-12px); }
        .bead.bottom-deck.b2.active { transform: translateY(-24px); }
        .bead.bottom-deck.b3.active { transform: translateY(-36px); }
        .bead.bottom-deck.b4.active { transform: translateY(-48px); }

        /* Right Column: Interaction Workspaces Dashboard */
        .dashboard-deck {
            display: flex;
            flex-direction: column;
            gap: 20px;
        }

        /* Operation Tab Selectors */
        .operation-tabs {
            display: grid;
            grid-template-columns: repeat(4, 1fr);
            gap: 6px;
            background: #f1f2f6;
            padding: 6px;
            border-radius: 14px;
        }

        .tab-btn {
            border: none;
            padding: 10px 5px;
            font-size: 1.1rem;
            font-weight: bold;
            border-radius: 10px;
            cursor: pointer;
            background: transparent;
            color: #7f8c8d;
            transition: all 0.2s ease;
        }
        .tab-btn.active {
            background-color: var(--container-bg);
            color: var(--accent-blue);
            box-shadow: 0 4px 10px rgba(0,0,0,0.05);
        }

        /* Question Panel card */
        .challenge-box {
            background: #fdfefe;
            border: 3px solid #dff9fb;
            border-radius: 18px;
            padding: 20px;
            text-align: center;
            box-shadow: 0 4px 12px rgba(0,0,0,0.02);
        }

        .math-problem-text {
            font-size: 3.2rem;
            font-weight: bold;
            color: var(--text-color);
            margin: 15px 0;
            letter-spacing: 2px;
        }

        .answer-form {
            display: flex;
            justify-content: center;
            align-items: center;
            gap: 12px;
            margin-top: 10px;
        }

        .input-box {
            width: 100px;
            height: 50px;
            font-size: 2rem;
            text-align: center;
            border: 3px solid var(--accent-blue);
            border-radius: 12px;
            outline: none;
        }

        .btn-action {
            border: none;
            color: white;
            font-size: 1rem;
            font-weight: bold;
            padding: 12px 22px;
            border-radius: 50px;
            cursor: pointer;
            transition: transform 0.1s ease, box-shadow 0.1s ease;
        }
        .btn-submit { background-color: var(--accent-blue); box-shadow: 0 4px #2980b9; }
        .btn-submit:active { transform: translateY(3px); box-shadow: none; }

        /* Bottom Section: Parent Dashboard Workspace Management */
        .parent-drawer {
            background-color: var(--parent-panel);
            border: 3px dashed #d35400;
            border-radius: 20px;
            padding: 20px;
            margin-top: 25px;
        }

        .parent-grid-controls {
            display: flex;
            justify-content: space-between;
            align-items: center;
            flex-wrap: wrap;
            gap: 15px;
            margin-top: 12px;
        }

        .parent-group {
            display: flex;
            align-items: center;
            gap: 10px;
            flex-wrap: wrap;
        }

        .parent-label {
            font-size: 0.85rem;
            font-weight: bold;
            color: #d35400;
            text-transform: uppercase;
            letter-spacing: 0.5px;
        }

        .parent-input {
            height: 38px;
            font-size: 1rem;
            padding: 5px 12px;
            border: 2px solid #d35400;
            border-radius: 8px;
            outline: none;
        }

        .btn-parent {
            background-color: #e67e22;
            color: white;
            border: none;
            padding: 9px 16px;
            font-weight: bold;
            border-radius: 8px;
            cursor: pointer;
            box-shadow: 0 3px #b35b10;
        }
        .btn-parent:active { transform: translateY(2px); box-shadow: 0 1px #b35b10; }
        .btn-download { background-color: #27ae60; box-shadow: 0 3px #1e7e43; }

        /* Notification Modals */
        .modal-screen {
            position: fixed;
            top: 0; left: 0; right: 0; bottom: 0;
            background: rgba(0,0,0,0.5);
            display: none;
            justify-content: center;
            align-items: center;
            z-index: 100;
        }
        .modal-card {
            background: white;
            padding: 40px;
            border-radius: 24px;
            text-align: center;
            width: 90%;
            max-width: 400px;
        }
        .modal-card h2 { font-size: 2.2rem; color: var(--accent-green); margin-bottom: 10px; }
        .modal-card p { font-size: 1.2rem; margin-bottom: 25px; }

        /* Responsive Adjustments */
        @media (max-width: 992px) {
            .grid-core {
                grid-template-columns: 1fr;
            }
        }

        @media (max-width: 768px) {
            body {
                padding: 100px 10px 20px 10px;
            }

            .lab-window {
                padding: 15px;
            }

            .greeting-banner {
                font-size: 1.2rem;
            }

            .badge {
                font-size: 0.9rem;
                padding: 6px 12px;
            }

            .abacus-frame {
                max-width: 380px;
                border-width: 10px;
            }

            .bead {
                width: 44px;
                height: 20px;
                left: -19px;
            }

            .rod {
                width: 4px;
            }

            .abacus-beam {
                height: 10px;
                top: 60px;
            }

            .bead.top-deck.active {
                transform: translateY(35px);
            }

            .math-problem-text {
                font-size: 2.5rem;
            }
        }

        @media (max-width: 480px) {
            .abacus-frame {
                max-width: 300px;
                border-width: 8px;
            }

            .bead {
                width: 34px;
                height: 18px;
                left: -15px;
            }

            .abacus-beam {
                top: 55px;
            }

            .bead.top-deck.active {
                transform: translateY(30px);
            }

            .bead.bottom-deck.b1 { top: 85px; }
            .bead.bottom-deck.b2 { top: 110px; }
            .bead.bottom-deck.b3 { top: 135px; }
            .bead.bottom-deck.b4 { top: 160px; }

            .abacus-rods-layer {
                height: 260px;
            }

            .tab-btn {
                font-size: 0.9rem;
            }

            .parent-grid-controls {
                flex-direction: column;
                align-items: stretch;
            }

            .parent-group {
                justify-content: center;
            }
        }