c# - C# Unity 更新和鼠标点击

Question

最近开始学习unity，遇到了一些看不懂的问题， 的值mouseClicked是false我一开始设置的，但是点击后我想设置为true，然后问题就开始了，打印出来mouseClicked 的值同时是真假，怎么可能呢？

public class Button1 : MonoBehaviour
{       
    float movespeed = 0.5f;
    float menuspeed = 5f;       
    bool mousEn = false;
    bool mouseClicked = false;      
    GameObject iconNew;
    GameObject dropQuad;        
    GameObject Mtx2;

    void Start () 
    {
        iconNew = GameObject.FindGameObjectWithTag("IconNew");
        dropQuad = GameObject.FindGameObjectWithTag("DropQuad1");           
        Mtx2 = GameObject.FindGameObjectWithTag("Mtxt2");        
    }       
    void Update ()
    {                   
        if (mousEn && transform.position.z>-0.3f)
        {
            transform.Translate(Vector3.back * movespeed * Time.deltaTime);
        }
        else if (!mousEn && transform.position.z<0f)
        {
            transform.Translate(Vector3.forward * movespeed * Time.deltaTime);  
        }           
        Debug.Log(mouseClicked); //both false and true          
        if (mouseClicked && Mtx2.transform.position.y>10f)
        {               
            Mtx2.transform.Translate(Vector3.down * menuspeed * Time.deltaTime);                
        }           
        else if (!mouseClicked && Mtx2.transform.position.y!=12f)
        {               
            Mtx2.transform.Translate(Vector3.up * menuspeed * Time.deltaTime);              
        }           
    }       
    void OnMouseEnter()
    {
        renderer.material.color = Color.gray;
        mousEn = true;      
    }       
    void OnMouseExit()
    {
        renderer.material.color = Color.white;
        mousEn = false;         
    }       
    void OnMouseDown ()
    {
        mouseClicked = !mouseClicked;
    }
}