matter-attractors-f/docs/examples/gravity.js

Unofficial updated version of matter-attractors (https://www.npmjs.com/package/matter-attractors)

// install plugin
Matter.use(
  'matter-wrap', // not required, just for demo
  'matter-attractors' // PLUGIN_NAME
);

var Example = Example || {};

Example.gravity = function() {
  var Engine = Matter.Engine,
    Render = Matter.Render,
    Runner = Matter.Runner,
    Body = Matter.Body,
    Common = Matter.Common,
    MouseConstraint = Matter.MouseConstraint,
    Mouse = Matter.Mouse,
    World = Matter.World,
    Bodies = Matter.Bodies;

  // create engine
  var engine = Engine.create(),
    world = engine.world;

  // create renderer
  var render = Render.create({
    element: document.body,
    engine: engine,
    options: {
      width: Math.min(document.documentElement.clientWidth, 1024),
      height: Math.min(document.documentElement.clientHeight, 1024)
    }
  });

  Render.run(render);

  // create runner
  var runner = Runner.create();
  Runner.run(runner, engine);

  // add bodies
  world.bodies = [];
  world.gravity.scale = 0;

  engine.timing.timeScale = 1.5;

  for (var i = 0; i < 150; i += 1) {
    var radius = Common.random(6, 10);

    var body = Bodies.circle(
      Common.random(10, render.options.width), 
      Common.random(10, render.options.height),
      radius,
      {
        mass: Common.random(10, 15),
        frictionAir: 0,
        plugin: {
          attractors: [
            // there is a built in helper function for Newtonian gravity!
            // you can find out how it works in index.js
            MatterAttractors.Attractors.gravity
          ],
          wrap: {
            min: { x: 0, y: 0 },
            max: { x: render.options.width, y: render.options.height }
          }
        }
      }
    );

    var speed = 5;

    Body.setVelocity(body, { 
      x: Common.random(-speed, speed), 
      y: Common.random(-speed, speed)
    });

    World.add(world, body);
  }

  // add mouse control
  var mouse = Mouse.create(render.canvas),
    mouseConstraint = MouseConstraint.create(engine, {
      mouse: mouse,
      constraint: {
        stiffness: 0.2,
        render: {
          visible: false
        }
      }
    });

  World.add(world, mouseConstraint);

  // keep the mouse in sync with rendering
  render.mouse = mouse;

  // context for MatterTools.Demo
  return {
    engine: engine,
    runner: runner,
    render: render,
    canvas: render.canvas,
    stop: function() {
      Matter.Render.stop(render);
      Matter.Runner.stop(runner);
    }
  };
};