def set_back(self, x: int, y: int, r: int, g: int, b: int) -> None:
        """Set the background color of one cell.

        Args:
            x (int): X position to change.
            y (int): Y position to change.
            r (int): Red background color, from 0 to 255.
            g (int): Green background color, from 0 to 255.
            b (int): Blue background color, from 0 to 255.
        """
        i = self.width * y + x
        self.back_r[i] = r
        self.back_g[i] = g
        self.back_b[i] = b
Set the background color of one cell.

        Args:
            x (int): X position to change.
            y (int): Y position to change.
            r (int): Red background color, from 0 to 255.
            g (int): Green background color, from 0 to 255.
            b (int): Blue background color, from 0 to 255.