// Daniel Shiffman

// http://natureofcode.com

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const { Engine, Bodies, Composite, Body, Vector }  = Matter;

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// A reference to the matter physics engine

let engine;

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// An array for all boxes

let boxes = [];

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// An array for all boundaries

let boundaries = [];

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function setup() {

  createCanvas(640, 240);

  // Create the Matter engine

  engine = Engine.create();

​

  // Add a bunch of fixed boundaries

  boundaries.push(new Boundary(width / 4, height - 5, width / 2 - 50, 10));

  boundaries.push(

    new Boundary((3 * width) / 4, height - 50, width / 2 - 50, 10)

  );

}

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function draw() {

  background(255);

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  // Update the engine!

  Engine.update(engine);

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  // Boxes fall from the top every so often

  if (random(1) < 0.1) {

    let b = new Box(width / 2, 50);

    boxes.push(b);

  }

​

  // Iterate over the boxes backwards

  for (let i = boxes.length-1; i >= 0; i--) {

    boxes[i].show();

    // Remove the Body from the world and the array

    if (boxes[i].checkEdge()) {

      boxes[i].removeBody();

      boxes.splice(i, 1);

    }

  }

  // Display all the boundaries

  for (let i = 0; i < boundaries.length; i++) {

    boundaries[i].show();

  }

}

​