在外面设置按键控制移动：

 using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class playcontrol : MonoBehaviour {

    public KeyCode upkey;//外面去指定键
    public KeyCode downkey;//外面去指定键
    public float speed = 10;//外面指定速度

    private AudioSource audio;
    private Rigidbody2D rigidbody2;
    // Use this for initialization
    void Start () {
        rigidbody2 = GetComponent<Rigidbody2D>();

        audio = GetComponent<AudioSource>();
    }
    
    // Update is called once per frame
    void Update () {
        if (Input.GetKey(upkey))
        {
            rigidbody2.velocity = new Vector2(0, speed);//赋予速度
        }
        else if(Input.GetKey(downkey))
        {
            rigidbody2.velocity = new Vector2(0, -speed);
        }
        else
        {
            rigidbody2.velocity = new Vector2(0, 0);
        }
    }

     void OnCollisionEnter2D()
    {
        audio.pitch = Random.Range(0.8f, 1.2f);//控制播放速度，为了更生动
        audio.Play();//播放
    }
}