// Example of using the Ball class.
   // We create three ball objects and use their
   // methods: display(), move(), and collide()
   // Exercise:
   //  First read an understand the entire program, including
   // the Ball class.
   // Then, try the following:
   // 1. Add another, fourth, Ball to the sketch, say of size 35
   //    in a color of your chosing.
   //    Use the display(), move() and collide() methods
   //    to check for collisions. Hint: You will have to
   //    collisions for evey pair of Ball objects.
   // 2. Modify the collide() methods so that when two
   //     balls collide, they swap 10% of their RGB color
   //     values.
   //
   Ball b1;
   Ball b2;
   Ball b3;

void setup() {
   size(600, 600);

 // Create balls
   b1 = new Ball();
   b2 = new Ball(10, color(45, 50, 250));
   b3 = new Ball(50, color(5, 108, 28));
   } // setup()

void draw() {
   background(255);

 //  draw the balls
   b1.display();
   b2.display();
   b3.display();
   
   // Move them
   b2.move();
   b1.move();
   b3.move();

 // check collisions
   b1.collide(b2);
   b1.collide(b3);
   b2.collide(b3);
   } // draw()