Ball b_ball;
Ball y_ball;
Ball r_ball;
void setup() {
  size(800, 800);
  background(0);
  b_ball = new Ball(50, 400, 100,2,2,color(0, 0,255));
  y_ball = new Ball(300, 200, 200,1,1,color(255,255, 0));
  r_ball = new Ball(700, 600, 100,3,3,color(255,0,0));
}

void draw() {
  background(0);
  b_ball.run();
  r_ball.run();
  y_ball.run();
}
class Ball {
  int x, y, diameter,radius, x_speed, y_speed, ball_color;
  Ball(int x_, int y_, int diameter_,int x_speed_, int y_speed_, int ball_color_) {
    x = x_;
    y = y_;
    diameter = diameter_;
    x_speed = x_speed_;
    y_speed = y_speed_;
    ball_color = ball_color_;
  }//close Ball constructor

  void run() {
    display();
    move();
    hit();
  }

  void display() {
    stroke(0);
    fill(ball_color);
    ellipse(x, y, diameter, diameter);
  }
  void move() {
    radius = diameter/2;
    if (x>=0&&y>=0) {
      x+=x_speed;
      y+=y_speed;
      if (x > width-radius || x < radius) {
        x_speed*=-1;
      }
      if (y > height-radius|| y < radius) {
        y_speed*=-1;
      }
    }
  }
  void hit(){
    if(collision()==true){
      r_ball.ball_color = 125;
      y_ball.ball_color = 125;
      b_ball.ball_color = 125;
    }
    else{
      r_ball.ball_color = color(255,0,0);
      y_ball.ball_color = color(255,255,0);
      b_ball.ball_color = color(0,0,255);
    }
  }
  boolean collision(){
    float dist_b_y,dist_y_r,dist_b_r;
    float dist_a,dist_b,dist_c;

    dist_b_y = (b_ball.x-y_ball.x)*(b_ball.x-y_ball.x)+(b_ball.y-y_ball.y)*(b_ball.y-y_ball.y);
    dist_a = sqrt(dist_b_y);

    dist_y_r = (y_ball.x-r_ball.x)*(y_ball.x-r_ball.x)+(y_ball.y-r_ball.y)*(y_ball.y-r_ball.y);
    dist_b = sqrt(dist_y_r);

    dist_b_r = (b_ball.x-r_ball.x)*(b_ball.x-r_ball.x)+(b_ball.y-r_ball.y)*(b_ball.y-r_ball.y);
    dist_c = sqrt(dist_b_r);

    if(dist_a-b_ball.radius<y_ball.radius){return true;}

    else if(dist_b-y_ball.radius<r_ball.radius){return true;}

    else if(dist_c-r_ball.radius<b_ball.radius){return true;}

    return false;
  }

}//close Ball class