Read-only properties provide insights into the quadrille’s current state and cannot be directly modified:

• mouseRow: The row index of the cell currently under the mouse pointer.
• mouseCol: The column index of the cell currently under the mouse pointer.
• size: The total number of cells in the quadrille.
• order: The number of non-empty cells in the quadrille.
• span: The smallest axis-aligned rectangle that contains all filled cells in the quadrille.