let pTransmission = 0.2; //on each collision

let pRecovery = 0.002; //on each screen draw

let pDeath = 0.0001; //on each screen draw

let numberOfBalls = 100; //increase this to make things more crowded

let diam = 20; //this also increases the chance of transmission

let pStayAtHome = 0.5; //increase this to flatten the curve!

​

​

let history = [];

let max = 0;

let graph = true;

​

let status = {

  "unexposed": "#000000",

  "infected": "#ff0000",

  "immune": "#00B000",

  "deceased": "#000090"

};

let balls = [];

​

function setup() {

  createCanvas(windowWidth, windowHeight);

  background(32);

  noStroke();

  for (var i = 0; i < numberOfBalls; i++) {

    balls[i] = new Ball(

      i, //ID number

      random(width), //start x coord

      random(height), //start y coord

      random(-10, 10), //start x velocity

      random(-10, 10), //start y velocity

      (i > pStayAtHome * numberOfBalls), //moving?

      balls //all the other balls

    );

  }

  frameRate(30);

  mouseClicked();

}

​

function draw() {

  background(192);

  for (i = 0; i < numberOfBalls; i++) {

    if (balls[i].stat != "deceased") {

      if (balls[i].moving) {

        balls[i].move();

      }

      balls[i].collide();

    }

    if (balls[i].stat == "infected") {

      if (random() < pRecovery) {

        balls[i].stat = "immune";

      } else if (random() < pDeath) {

        balls[i].stat = "deceased";

      }

    }

    balls[i].display();

  }

  history.push(count());

  if (graph) {

    plotGraph();

  }

  if (count()==0) {

    noLoop();

  }

}

​

function mouseClicked() {

  var thisOne = floor(random(numberOfBalls));

  balls[thisOne].stat = "infected";

}

​

function count() {

  var total = 0;

  for (var i = 0; i < numberOfBalls; i++) {

    if (balls[i].stat == "infected") {

      total++;

    }

  }

  if (total>max){

    console.log("maximum",total);

    max = total;

  }

  return total;

}

​

function plotGraph() {

    noFill();

    stroke(color(status["infected"]));

    beginShape();

    for (var i = 0; i < width; i++) {

      vertex(i, height - height * history[history.length - width + i] / numberOfBalls);

    }

    endShape();

    noStroke();

}

​

class Ball {

  constructor(

    id_ = 0,

    x_ = width / 2,

    y_ = height / 2,

    vx_ = random(-10, 10),

    vy_ = random(-10, 10),

    moving_ = true,

    others_= []) {

    this.id = id_;

    this.x = x_;

    this.y = y_;

    this.vx = vx_;

    this.vy = vy_;

    this.moving = moving_;

    this.others = others_;

    this.stat = "unexposed";

  }

  move() {

    if (this.x < 0 || this.x > width) {

      this.vx = -1 * this.vx;

    }

    if (this.y < 0 || this.y > height) {

      this.vy = -1 * this.vy;

    }

    this.x += this.vx;

    this.y += this.vy;

  }

​

  collide() {

    for (var i = this.id + 1; i < numberOfBalls; i++) {

      var dx = this.others[i].x - this.x;

      var dy = this.others[i].y - this.y;

      var dist = sqrt(dx * dx + dy * dy);

      if (dist < 0.71 * diam) {

        if (random() < pTransmission) {

          if (this.stat == "infected" && this.others[i].stat == "unexposed") {

            this.others[i].stat = "infected";

          }

          if (this.stat == "unexposed" && this.others[i].stat == "infected") {

            this.stat = "infected";

          }

        }

      }

    }

  }

​

  display() {

    fill(color(status[this.stat]));

    ellipse(this.x, this.y, diam / 2, diam / 2);

  }

}