let ps;

​

function setup() {

  createCanvas(windowWidth, windowHeight);

​

  radius = 8;

​

  ps = [];

  for (let c = 0; c < radius; c++) {

    ps.push({

      loc: createVector(

        random(radius, width - radius),

        random(radius, height - radius)

      ),

      vel: createVector(random(-1, 1), random(-1, 1)),

    });

  }

​

  ps.push({

    loc: createVector(

      random(radius, width - radius),

      random(radius, height - radius)

    ),

    vel: createVector(random(-3, 3), random(-3, 3)),

  });

}

​

function draw() {

  background(220, 20, 120);

​

  fill(255);

  stroke(0);

  strokeWeight(1);

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

    let p = ps[i];

    if (p.loc.x < radius || p.loc.x > width - radius) {

      p.vel.x *= -1;

    }

    if (p.loc.y < radius || p.loc.y > height - radius) {

      p.vel.y *= -1;

    }

​

    p.loc.add(p.vel);

​

    let xAxis = createVector(1, 0);

    let hAngle = xAxis.angleBetween(p.vel);

​

    push();

    translate(p.loc.x, p.loc.y);

    rotate(hAngle);

    triangle(-radius, radius, -radius, -radius, 2 * radius, 0);

    pop();

  }

}

​