Pointy Prism - RobotC Lego NXT code

pointyprism.c

void makeCircle(int _cx,int _cy,int _rad) {
int l=_cx-_rad;
int r=_cx+_rad;
int u=_cy+_rad;
int d=_cy-_rad;
nxtFillEllipse (l,  u,r,  d);
}
void eraseCircle(int _cx,int _cy,int _rad) {
int l=_cx-_rad;
int r=_cx+_rad;
int u=_cy+_rad;
int d=_cy-_rad;
nxtEraseEllipse (l,  u,r,  d);
}

task main () {

// 4th line ~ 8 lines, 0-7.
nxtDisplayString (4," Hello World !");
wait1Msec (100);

int cx,cy,rad,x,y,cxx,cyy;
int flop;




x=0;
y=0;

while (1) {
//	if (cxx>3 || cxx<-3){
   eraseDisplay();
cx=50;
cy=32;
rad=40;
flop=0;

while(rad>0) {
makeCircle(cx,cy,rad);
  if (rad==30)wait1Msec (10);
    if (rad==20)wait1Msec (10);
      if (rad==2)wait1Msec (100);
rad-=1;
if (flop==1){
cy+=cyy;}


eraseCircle(cx,cy,rad);
rad-=1;
if (flop==2){flop=0;}
if (flop==1){flop=2;}
if (flop==0){
cx+=cxx;
flop=1;}


}

x+=8;
y+=6;
cxx=5*sinDegrees(x);
cyy=5*cosDegrees(y);

//nxtDisplayBigStringAt (29 ,41 ,(string)x);
wait1Msec (10);
}


//nxtSetPixel(x,y);

wait1Msec (1000);
nxtDisplayBigStringAt (29 ,41 ,"Boo!");
wait1Msec (8000);

}