如何使一类对象朝不同的方向前进？

Question

我正在尝试使6条鱼（左侧3条，右侧3条）彼此靠近。

我不太确定该怎么做。

下面的代码使6条鱼全部转圈，我想使用一个if语句，这样，当某事发生时（例如，屏幕上随机出现某物（chicken.leg！= null），鱼将停止转圈）并开始移向屏幕上出现的对象。

public override void Update(ref GameTime pGameTime)
{
    Vector3 tokenPosition = this.PossessedToken.Position;
    tokenPosition.X = tokenPosition.X + xSpeed;
    this.PossessedToken.Position = tokenPosition;
    this.PossessedToken.Orientation = new Vector3(mFacingDirectionX,
                                            this.PossessedToken.Orientation.Y,
                                            this.PossessedToken.Orientation.Z);

    tokenPosition.Y = tokenPosition.Y + ySpeed;
    this.PossessedToken.Position = tokenPosition;
    this.PossessedToken.Orientation = new Vector3(mFacingDirectionX,
                                            this.PossessedToken.Orientation.Y,
                                            this.PossessedToken.Orientation.Z);

    if (tokenPosition.X == -280 || tokenPosition.X == 320)
    {
        xSpeed = 1;
        ySpeed = -1;
    }

    if (tokenPosition.Y == 120 || tokenPosition.Y == -180 || tokenPosition.Y == -30)
    {
        xSpeed = -1;
        ySpeed = 0;
    }

    if (tokenPosition.X == -300 || tokenPosition.X == 300)
    {
        xSpeed = 1;
        ySpeed = 1;
    }

    if (mAquarium.ChickenLeg != null)
    {
        xSpeed = 1;
    }
}

我希望使用一堂课，左边的3条鱼向右走，右边的3条鱼向左走。