// An array of Shape objects; remember, we can put any object in here
// that inherits from the Shape class.
Shape[] shapes = new Shape[25];

void setup() {

    // setup the environment
    size(400, 400);
    colorMode(RGB, 255, 255, 255, 255);
    smooth();
    
    // Create 25 Shapes, a random selection of circles and square
    for (int i = 0; i < shapes.length; i++) {
    
        int rand = int(random(2));
        if (rand ==0) {
            shapes[i] = new Circle(200, 200, 10, color(32, 64, 128));
        } else {
            shapes[i] = new Square(200, 200, 10);
        }
    }
}

void draw() {

    // clear the background
    background(0);
    
    // Because both Circle and Square are shape objects,
    // we can treat all of the objects in the shapes array
    // the same. The correct shake() and render() methods will
    // be called for each kind of shape
    for (int i = 0; i < shapes.length; i++) {
    
        Shape myShape = shapes[i];
        myShape.shake();
        myShape.render();
    }
}