constructor(width, height) {

    this.scale = 1.0;

    this.objects = [];

    this.width = width;

    this.height = height;

    this.cx = width / 2;

    this.cy = height / 2;

  }

​

  setScale(scale) {

    this.scale = scale;

  }

​

  addObject(pos, radius, name, r = 255, g = 255, b = 255) {

    var obj = {

      x: pos.x,

      y: pos.y,

      r: radius,

      color: {

        r: r,

        g: g,

        b: b

      },

      text: name

    };

    this.objects.push(obj);

  }

​

  draw() {

    for (var i = 0; i < this.objects.length; ++i) {

      //print('The value of scale is ' + this.scale);

      var obj = this.objects[i];

      var x = obj.x * this.scale;

      var y = obj.y * this.scale;

      var r = obj.r * this.scale;

      stroke(obj.color.r, obj.color.g, obj.color.b);

      fill(obj.color.r, obj.color.g, obj.color.b);

      circle(this.cx + x, this.cy + y, r);

​

      //

      textFont('Helvetica');

      strokeWeight(1);

      stroke(255, 255, 255);

      fill(255, 255, 255);

      textSize(15);

      text(obj.text, this.cx + x - 20, this.cy + y - 15);

    }

  }

}

​

var CanvasWidth = 1200;

var CanvasHeight = 750;

var MaxInvScale = 1000000;

var MinInvScale = 1;

let myapp = new UniverseApp(CanvasWidth, CanvasHeight);

let slider;

​

function setup() {

  // create the scaleSlider

  slider = createSlider(MinInvScale, MaxInvScale, 500);

  slider.position(10, 10);

  slider.style('width', '450px');

  background(0, 0, 0);

  // objects

  var pos = {

    x: 0,

    y: 0

  };

  myapp.addObject(pos, 695510, "Sun", 255, 0, 0);

  myapp.addObject({x: 1496000000, y: 0}, 6371, "Earth", 0, 0, 255);

  //

  createCanvas(1200, 750);

}

​

function draw() {

  background(0, 0, 0);

  //scale the universe

  let val = slider.value();

  var uni_scale = 0.001 / val;

  myapp.setScale(uni_scale);

  textFont('Helvetica');

  strokeWeight(1);

  stroke(255, 255, 255);

  fill(255, 255, 255);

  textSize(20);

  var scaleText = "Scale (pixel to Km) : " + uni_scale.toFixed(10);

  text(scaleText, 15, 60);

​

  // draw the universe

  myapp.draw();

}