class Ball {

  ArrayList<Ball> others;
  PVector pos, vel, acc, siz;
  PImage img;
  color col = color(255, 0, 0);
  float startSpeed = 5;

  float maxSpeed = 10;
  int posMode = CENTER;
  boolean gravity = false;
  boolean bounded = true;
  boolean selfReflect = true;
  boolean speedEnforced = true;
  boolean offScreen = false;

  public Ball() {
    pos = new PVector(width/2, height/2);
    vel = new PVector(-5, 5);
    siz = new PVector(40, 40);
    vel.limit(startSpeed);
  }

  public Ball(PVector start) {
    pos = start;
    vel = new PVector(-5, 5);
    siz = new PVector(40, 40);
    vel.limit(startSpeed);
  }

  public Ball(PVector start, PVector startVel) {
    pos = start;
    vel = startVel;
    siz = new PVector(40, 40);
    vel.limit(startSpeed);
  }
  public Ball(PVector start, PVector startVel, color _col) {
    pos = start;
    vel = startVel;
    siz = new PVector(40, 40);
    vel.limit(startSpeed);
    col = _col;
  }

  public Ball(ArrayList<Ball> _others, PVector start, PVector startVel, color _col) {
    others = _others;
    pos = start;
    vel = startVel;
    siz = new PVector(40, 40);
    vel.limit(startSpeed);
    col = _col;
  }

  void update() {
    //vel.add(acc);
    pos.add(vel);
  }

  void check() {
    if (speedEnforced) {
      vel.limit(maxSpeed);
    }
    if (bounded) {
      if (abs(pos.x - width/2)>width/2-siz.x/2) {
        //undo last step
        pos.sub(vel);
        vel.x*=-1;
        pos.add(vel);
      }
      if (abs(pos.y - height/2)>height/2-siz.y/2) {
        //undo last step
        pos.sub(vel);
        vel.y*=-1;
        pos.add(vel);
      }
    }
    else{
      //if the ball is not bounded by the screen and it leaves far enough, remove it
       offScreen = (abs(pos.x - width/2)>width/2-siz.x/2)&&(abs(pos.y - height/2)>height/2-siz.y/2);
       //Move responibility to removal to outside of class for safety
       //if (offScreen &&others != null){
       //    others.remove(this);
       //}

    }
    //check other balls
    if (selfReflect && others != null) {
      for (Ball b : others) {
        if (b != this) {//don't let it bounce with it self
          if (pos.dist(b.pos)< (siz.x+b.siz.x)/2) {
            PVector normal = PVector.sub(b.pos, pos);
            float theta = PVector.angleBetween(vel, normal);
            //draw an effect at the point of impact
            //hitEffectPos = temp;
            //starting size
            //hitEffectSize = 5;
            //remove the last step (?)
            //bPos.sub(bVel);
            //apply the angle of reflection
            vel.rotate(-2*theta);
            pos.add(vel);
            theta = PVector.angleBetween( normal,b.vel);
            b.vel.rotate(2*theta);
            b.pos.add(b.vel);
            //move the

          }
        }
      }
    }
  }

  void draw() {
    fill(col);
    ellipse(pos.x, pos.y, siz.x, siz.y);
  }
}