想用C / C ++移动球

#include<graphics.h>
#include<conio.h>
#include<alloc.h>
#include<dos.h>
#include<stdlib.h>

void *ball;

void image()
{
    setcolor(RED);
    setfillstyle(SOLID_FILL,RED);
    fillellipse(10,10,10,10);
    ball=malloc(imagesize(0,0,20,20));
    getimage(0,0,20,20,ball);
    cleardevice();
}

void main(void)
{
    int gmode,gdriver=DETECT;
    initgraph(&gdriver,&gmode,"c:\\tc\\bgi");

    int l=getmaxx()/2,r=0,t=0,b=0;
    int x=1,y=1;
    int s=0,key=0;
    int xstep=1,ystep=1;

    image();
    setbkcolor(GREEN);

    while(key!=27)
    {
        while(!kbhit())
        {
            outtextxy(250,350,"");
            setcolor(7);

            putimage(l,t,ball,XOR_PUT);
            delay(5);
            putimage(l,t,ball,XOR_PUT);

            if(l>=getmaxx()||l<=0)
            {
                x*=-1;sound(1000);
                s=0;xstep=x*(random(4) 1);
                ystep=y*(random(3) 1);
                if(l<=0)
                    l=0;
                else
                    l=getmaxx();
            }

            if(t>=getmaxy()||t<=0)
            {
                y*=-1;sound(1000);
                s=0;ystep=y*(random(4) 1);
                xstep=x*(random(3) 1);
                if(t<=0)
                    t=0;
                else
                    t=getmaxy();
            }

            l =x xstep;
            t =y ystep;
            s  ;

            if(s==5)
            {
                nosound();
            }
        }

        key=getch();
    }

    closegraph();
}

这个球随机移动，但我想把这个球向左（中），右（中），向上（中），向下移动（中心）像钻石<>

This ball moves randomly, but I would like to move this ball just left(center), right(center), up(center), down(center) like diamond <>