alpha = 360,

  G = 6.67408, // Universal gravitational constant

  particles = [],

  trails = false;

​

function setup() {

  createCanvas(window.innerWidth, window.innerHeight);

  colorMode(HSB, 360);

  background(5);

}

​

function draw() {

  if (!trails) background(5);

  let bestVel = 0;

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

    for (let j = 0; j < particles.length; j++) {

      if (particles[i] !== particles[j]) {

        particles[i].attracted(particles[j]);

      }

    }

    particles[i].update();

    particles[i].show();

    const tV = abs(particles[i].vel.x + particles[i].vel.y);

    if (tV > bestVel) {

      bestVel = tV;

    }

  }

  maxVel = bestVel;

​

  noStroke();

  fill(255);

  textSize(16);

  text("click to add a particle", 0, height - 65);

  text("particles are attracted to each other", 0, height - 45);

  text("t to toggle trails", 0, height - 25);

  text("r to reset", 0, height - 5);

}

​

function keyPressed() {

  if (key === "t") {

    trails = !trails;

  } else if (key === "r") {

    particles = [];

  }

}

​

function mousePressed(e) {

  particles.push(new Particle(mouseX, mouseY, true));

}

​