視覺欺騙

#include <graphics.h>
#include <stdio.h>
#include<math.h>
void main(void)
{
   int gdriver = DETECT, gmode, errorcode;
   int i,j,midx,midy;
   double r;
   initgraph(&gdriver, &gmode, "");
   errorcode = graphresult();
   if (errorcode != grOk)
   {
      printf("Graphics error: %s\n", grapherrormsg(errorcode));
      printf("Press any key to halt:");
      getch();
      exit(1);
   }
   midx=getmaxx()/2;
   midy=getmaxy()/2;
   setcolor(14);
   for(i=1;i<=140;i+=10)
     circle(midx,midy,i);
   setcolor(14);
   rectangle(midx-70,midy-70,midx+70,midy+70);
   getch();
   cleardevice();
   setfillstyle(1,7);
   for(i=20;i<=2*midx;i+=20)
   {
     bar(i,0,i+4,2*midy);
	 if(i<=2*midy)
	    bar(0,i,2*midx,i+4);	 
   }
   setcolor(15);
   setfillstyle(1,15);   
   for(i=22;i<2*midx;i+=20)
   {
     for(j=22;j<=2*midy;j+=20)
	 {
	   circle(i,j,3);
	   floodfill(i,j,15);
	 }
   }
   getch();
   closegraph();
 }