代码中有一个地方看不懂为什么？关于按键的，大家看看吧

int CSnake::keyPress(int key)        //按键控制
{
    if(up&&key == 72)     //return 5只是一种标记，代表此时要发设子弹                                                                                                                             
        return 5 ;
    if(down&&key == 80)
        return 5 ;
    if(left&&key == 75)
        return 5 ;
    if(right&&key ==77)
        return 5 ;
    if((up==true)&&(key==115||key==80))
        return 6;//反向向下
    if((down == true)&&(key == 119||key==72))
        return 6;//反向向上
    if((right==true)&&(key == 97||key == 75))
        return 6;//反向向左
    if((left==true)&&(key == 100||key == 77))
        return 6;//反向向右
    if(key!=224)        //根据传入的键值来判断方向
    {
        if((key == 119||key==72)&&down!=true)            //UP
        {
            up = true ;
            down = left = right = false ;
        }
        if((key == 115||key == 80)&&up!= true)            //DOWN
        {
            down = true ;
            right = up = left = false ;
        }
        if((key ==  97||key == 75)&&right !=true)            //LEFT
        {
            left = true ;
            right = up = down = false;
        }
        if((key == 100||key == 77)&&left !=true)            //RIGHT
        {
            right = true  ;
            left = up = down = false;
        }
        

    }
    return 0 ;
}