// author: didier hilhorst
// p5_version: 0068

BImage b;

float xoff = 0.0; 

Circle cir1, cir2, cir3, cir4, cir5; 

void setup() {
  size(500, 500);
  noStroke();
  
  b = loadImage("bg_elas.gif");
  
  xoff = xoff + .01; 
  float n = noise(xoff) * 2; // experimenting with this...
  
  cir1 = new Circle(mouseX, mouseY, 60, 60);
  cir1._inertia = 0.9;
  cir1._k = n;
  cir1._r = 119;
  cir1._g = 119;
  cir1._b = 119;

  cir2 = new Circle(mouseX, mouseY, 50, 50);
  cir2._inertia = 0.88;
  cir2._k = n;
  cir2._r = 153;
  cir2._g = 153;
  cir2._b = 153;

  cir3 = new Circle(mouseX, mouseY, 40, 40);
  cir3._inertia = 0.86;
  cir3._k = n;
  cir3._r = 187;
  cir3._g = 187;
  cir3._b = 187;

  cir4 = new Circle(mouseX, mouseY, 30, 30); // small_pink_circle (color only)
  cir4._inertia = 0.84;
  cir4._k = n;
  cir4._r = 255;
  cir4._g = 102;
  cir4._b = 153;
  
  cir5 = new Circle(mouseX, mouseY, 20, 20);
  cir5._inertia = 0.82;
  cir5._k = n;
  cir5._r = 85;
  cir5._g = 85;
  cir5._b = 85;

}

void loop() {
  background(b);
  cir1.elasPosition(mouseX-30, mouseY-30);
  cir2.elasPosition(mouseX-25, mouseY-25);
  cir3.elasPosition(mouseX-20, mouseY-20);
  cir4.elasPosition(mouseX-15, mouseY-15);
  cir5.elasPosition(mouseX-10, mouseY-10);
}

class Circle {
  float _x, _y, _width, _height, _inertia, _k, vx, vy, _r, _g, _b;
  Circle(float x, float y, float w, float h) {
    _x = x;
    _y = y;
    _width = w;
    _height = h;
    _inertia = 0.92;
    _k = 0.1;
    _r = 85;
    _g = 85;
    _b = 85;
    fill(_r, _g, _b);
    render();
  }

  void render() {
    smooth();
    ellipse(_x, _y, _width, _height);
    fill(_r, _g, _b);
  }

  void setPosition(float x, float y) {
    _x = x;
    _y = y;
    render();
  }

  void elasPosition(float x, float y) {
    float tx = _x;
    float ty = _y;
    float dx = x - tx;
    float dy = y - ty;
    float ax = dx*_k;
    float ay = dy*_k;
    vx = vx + ax;
    vy = vy + ay;
    vx = vx * _inertia;
    vy = vy * _inertia;
    tx = tx + vx;
    ty = ty + vy;
    setPosition(tx, ty);
  }
}