// Daniel Shiffman

// http://natureofcode.com

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// Reference to physics world

var physics;

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var p1;

var p2;

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function setup() {

  createCanvas(640,360);

​

  // Initialize the physics

  physics=new VerletPhysics2D();

  physics.addBehavior(new GravityBehavior(new Vec2D(0,0.5)));

​

  // Set the world's bounding box

  physics.setWorldBounds(new Rect(0,0,width,height));

  // Make two particles

  p1 = new Particle(new Vec2D(width/2,20));

  p2 = new Particle(new Vec2D(width/2+160,20));

  // Lock one in place

  p1.lock();

​

  // Make a spring connecting both Particles

  var spring=new VerletSpring2D(p1,p2,160,0.01);

​

  // Anything we make, we have to add into the physics world

  physics.addParticle(p1);

  physics.addParticle(p2);

  physics.addSpring(spring);

}

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function draw() {

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  // Update the physics world

  physics.update();

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  background(0);

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  // Draw a line between the particles

  stroke(200);

  strokeWeight(2);

  line(p1.x,p1.y,p2.x,p2.y);

​

  // Display the particles

  p1.display();

  p2.display();

​

  // Move the second one according to the mouse

  if (mouseIsPressed) {

    p2.lock();

    p2.x = mouseX;

    p2.y = mouseY;

    p2.unlock();

  } 

}

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