long max(long i, long j) {
  return (i>j)?i:j;  
}
boolean even(int i) {
  return round(i*.5) == (i/2); 
}

public void drawArrow( float x, float y, float dx, float dy, float r, int c1) {
  stroke(c1);
  float l = sqrt(sq(dx) + sq(dy));
  if (l>0) {
    dx = dx/l*r;
    dy = dy/l*r;
    line(x,y,x - dx,y - dy);
    line(x,y,x-dx/2-dy/2,y-dy/2 + dx/2);
    line(x,y,x-dx/2+dy/2,y-dy/2 - dx/2);
  }
}

public void drawDart( float x, float y, float dx, float dy, float r, int c1) {
  fill(c1);
  noStroke();
  float l = sqrt(sq(dx) + sq(dy));
  if (l>0) {
    dx = dx/l*r;
    dy = dy/l*r;
    beginShape();
    vertex(x,y);
    vertex(x-dx-dy/2,y-dy + dx/2);
    vertex(x-dx+dy/2,y-dy - dx/2);
    endShape(CLOSE);
  }
}