// ifs
int x,y;

float f,fctr;
float angint;
int mode, modecnt;


ifs(int x, int y, float ang, float scle) {
  int nx, ny,a,n;
  float r;
  nx=x+cos(ang)*scle; 
  ny=y+sin(ang)*scle;

  scle = scle / fctr;
  line(1,x,y,nx,ny);
  
  if(scle>0.8){
    if(mode==0){ // tree
ifs(nx,ny,ang-angint-(rand()-0.5),scle*((rand()*1.2)));
ifs(nx,ny,ang+angint+(rand()-0.5),scle*((rand()*1.2)));

    } else{
     if(mode == 1){ //fern

ifs(nx,ny,ang-0.5,scle);
ifs(nx-(nx-x)*0.4,ny-(ny-y)*0.4,ang+0.5,scle*((rand()*0.6+0.3)));
ifs(nx-(nx-x)*0.9,ny-(ny-y)*0.9,ang+0.5,scle*((rand()*0.6+0.3)));
ifs(nx-(nx-x)*0.6,ny-(ny-y)*0.6,ang-0.5,scle*((rand()*0.6+0.3)));
//ifs(nx-(nx-x)*0.2,ny-(ny-y)*0.2,ang-0.5,scle*((rand()*0.6+0.3)));
     }else{
       if(mode == 2){ //
	ifs(nx,ny,ang-angint - (rand()-0.5), scle*((rand()*1.0 + 0.2)));
	ifs(nx,ny,ang+angint + (rand()-0.5), scle*((rand() * 1.0 + 0.2)));
r=rand()*0.6;
ifs(nx-(nx-x)*r,ny-(ny-y)*r,ang-0.5,scle*((rand()*0.6+0.3)));
r=rand()*0.6;
ifs(nx-(nx-x)*r,ny-(ny-y)*r,ang+0.5,scle*((rand()*0.6+0.3)));
       }
     }
    }
  }
}
draw() {
   int e;
   float iang, ilen;
    int xx, yy;
   // Get initial position
   x = penx();
   y = peny();

   // Draw lines until we stop receiving penMoves
do {

      xx = penx();
      yy = peny();
   } while (event(1)==4);
      ilen =  sqrt(pow((x - xx),2) + pow((y - yy),2));
    if(ilen == 0 || (xx - x) == 0){return;}

    iang = atan((yy - y)/((float)xx - x));     
  if((xx-x)<0){
    iang = iang + 3.141592;
  } 
      ifs(x, y, iang, ilen);
}

main() {
  int e;
   mode=0;
   modecnt=3;
   angint = 3.141592 / 5;
   fctr = 1.7;
   graph_on();
   title("IFS");
   while (1) {
      e = event(1);
      if (e==5){
	mode++;
          mode = mode % modecnt;
      }else{
      if (e==6){
   clear();
      }else{

      if (e==2) draw();
     }
    }
   }
}