tml += '</tr>';
            }
            html += '</tbody></table></div>';
            
            return html;
        }
        
        // Cell manipulation
        function runCellAndSelectBelow(cellId) {
            runCell(cellId);
            selectNextCell(cellId);
        }
        
        function runCellAndInsertBelow(cellId) {
            runCell(cellId);
            addCellAfter(cellId);
        }
        
        function addCell() {
            const cellId = `cell-${Date.now()}`;
        