Roll A Ball

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

public class FollowPlayer : MonoBehaviour
{
    public GameObject player;

    // Update is called once per frame
    void Update()
    {
        Vector3 player_position = player.GetComponent<Transform>().position;
        this.GetComponent<Transform>().position = new Vector3(player_position.x, player_position.y + 13.14f, player_position.z - 13.98f);
    }
}

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

public class food : MonoBehaviour
{
    // Update is called once per frame
    void Update()
    {
        this.transform.Rotate(Vector3.up);                        //此处transform小写！
    }
}

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

public class Player : MonoBehaviour
{
    int i = 0;
    // Update is called once per frame
    void Update()
    {
        float horizontal_move = Input.GetAxis("Horizontal");   //horizontal必须与unity名称一模一样！
        float vertical_move = Input.GetAxis("Vertical");  //unity位置：Edit-Projectings-Input
        this.GetComponent<Rigidbody>().AddForce(new Vector3(horizontal_move, 0, vertical_move) * 10);
    }

    void OnTriggerEnter(Collider other)     //OnTriggerEnter是一个方法，且i不能定义在它里面，每次调用这个方法，i都会被初始化！
    {
        if (other.gameObject.name == "food")
        {                                         //i不能定义在这里面！因为if每次都会将i初始化为0，永远都不可能“win”！
            GameObject.Destroy(other.gameObject);
            i++;
            if (i == 10)
            {
                Debug.Log("U are win ! ");
            }
        }
    }
}