def __init__(
        self,
        position_x: float,
        position_y: float,
        velocity_x: float,
        velocity_y: float,
        mass: float = 1.0,
        size: float = 1.0,
        color: str = "blue",
    ) -> None:
        self.position_x = position_x
        self.position_y = position_y
        self.velocity_x = velocity_x
        self.velocity_y = velocity_y
        self.mass = mass
        self.size = size
        self.color = color