Flyer[] flyers = new Flyer[5];

void setup(){
  size(200, 200);

  for(int i = 0; i < flyers.length; i++){
    flyers[i] = new Flyer();
  }
}

void draw(){
  background(200);

  for(int i = 0; i < flyers.length; i++){
   flyers[i].step();
   flyers[i].draw();
  }
}

class Flyer{

  float x = random(width);
  float y = random(height);
  float heading = random(TWO_PI);
  float speed = random(1, 3);  
  float radius = random(5, 20);

  void step(){

    float angleToMouse = atan2(mouseY-y, mouseX-x);

    //prevent case where heading is 350 and angleToMouse is 10
    if(heading-angleToMouse > PI){
      angleToMouse += TWO_PI;
    }
    else if(angleToMouse-heading > PI){
      angleToMouse -= TWO_PI;
    }

    //turn towards mouse
    if(heading < angleToMouse){
      heading+=PI/50;
    }
    else{
      heading-=PI/50;
    }

    //move in direction
    x += cos(heading)*speed;
    y += sin(heading)*speed;

    //wrap around edges
    if(x < 0){
      x = width;
    }
    if(x > width){
      x = 0;
    }

    if(y < 0){
      y = height;
    }
    if(y > height){
      y = 0;
    }

  }

  void draw(){
    ellipse(x, y, radius, radius);
  }

}