enum:

    //移动枚举
    public enum STEP
    {
        NONE = -1,
        RUN = 0,            //奔跑 游戏中
        STOP,               //停止 显示得分时
        MISS,               //失败 和怪物解除
        NUM,
    };

Update：

//各个状态的执行

        //位置
        switch (this.step)
        {
            case STEP.RUN:
                {
                    //速度
                    if (this.is_running)
                    {
                        this.run_speed += OwnPlayerControl.run_speed_add * Time.deltaTime;
                    }
                    else
                    {
                        //减速
                    }
                    this.run_speed = Mathf.Clamp(this.run_speed, 0.0f, RUN_SPEED_MAX);

                    //应用于本rigidbody的velocity
                    Vector3 new_velocity = this.GetComponent<Rigidbody>().velocity;
                    new_velocity.x = run_speed;

                    //y坐标速度不变
                    if (new_velocity.y > 0.0f)
                    {
                        new_velocity.y = 0.0f;
                    }

                    //应用new_velocity
                    this.GetComponent<Rigidbody>().velocity = new_velocity;//Vector3

                    //按W键快速前进 用于调试
                    if (Input.GetKeyDown(KeyCode.W))
                    {
                        Vector3 new_position = this.transform.position;
                        new_position.x += 100*OwnFloorControl.WIDTH * OwnFloorControl.MODEL_NUM;
                        this.transform.position = new_position;
                    }

                    //按space空格跳跃 用于调试
                    if (Input.GetKeyDown(KeyCode.Space))
                    {
                        Vector3 new_position = this.transform.position;
                        new_position.y += JUMP_HEIGHT;
                        this.transform.position = new_position;
           
                    }
                }
                break;