body {
  margin: 0;
  padding: 0;
}

let stars;

const limitSpeed = true;
const canvasWidth = 400;
const canvasHeight = 150;

function setup() {
  createCanvas(canvasWidth, canvasHeight);
  stars = [];
  for (let i = 0; i < 3; i++) {
    const star = createBody(random(width/2), random(height), 300);
    star.setColor("yellow");
    star.setSize(30);
    stars.push(star);
  }
  for (let i=0; i<3; i++) {
    const star = createBody(stars[i].position.x + width/2, stars[i].position.y, 300);
    star.setColor("green");
    star.setSize(30);
    stars.push(star);
  }
  stars[5].position.x += 1;
}

function draw() {
  background(150);
  stroke(0);
  line(width/2, 0, width/2, height);
  for (let i = 0; i < 3; i++) {
    for (let j = 0; j < 3; j++) {
      if (i !== j) {
        stars[j].attract(stars[i]);
      }
    }
    stars[i].update();
    stars[i].show();
    
  }
  
  for (let i=3; i < 6; i++) {
    for (let j=3; j<6; j++) {
      if (i!= j) {
        stars[j].attract(stars[i]);
      }
    }
    stars[i].update();
    stars[i].show();      
  }
  
}

function createBody(x, y, mass) {
  const position = createVector(x, y);
  const velocity = createVector(0, 0);
  const acceleration = createVector(0, 0);
  const G = 0.001;
  let fillColor = "white";
  let size = 50;

  const applyForce = (force) => {
    const a = p5.Vector.div(force, mass);
    acceleration.add(a);
  };

  const attract = (body) => {
    const force = p5.Vector.sub(position, body.position);
    let distance = force.mag();
    if (limitSpeed) {
      distance = constrain(distance, 5, 25);
    }
    let strength = (G * mass * body.mass) / (distance * distance);
    force.setMag(strength);
    body.applyForce(force);
  };

  const update = () => {
    velocity.add(acceleration);
    position.add(velocity);
    acceleration.mult(0);
  };

  const show = () => {
    stroke(0);
    fill(fillColor);
    circle(position.x, position.y, size);
  };

  const setColor = (c) => {
    fillColor = c;
  };

  const setSize = (s) => {
    size = s;
  };

  return {
    position,
    mass,
    applyForce,
    attract,
    update,
    show,
    setColor,
    setSize
  };
}