x: 200,

  y: 30,

  radius: 20,

  display(){

    rect(0,0,windowWidth,this.y+this.radius);

    line(0,this.y+this.radius,windowWidth,this.y+this.radius);

    line(30,this.y,windowWidth-30,this.y);

    ellipse(this.x,this.y,this.radius,this.radius);

  }

}

let probConstant;

let dragMode = false;

​

function setup() {

  createCanvas(windowWidth, windowHeight);

  frameRate(25);

  background(220);

  probConstant = (slider.x-30)*1024/windowWidth;

}

​

function draw() {

  slider.display();

  if (mouseIsPressed){

    if (!(onSlider() || dragMode))

      splotch();

    else

      dragSlider();

  }

}

​

function splotch(){

  for (let i=-50; i<50; i++){

    for (let j=-50; j<50; j++){

      let dist = sqrt(i**2 + j**2);

      if (Math.random() < prob(dist) && mouseY+j > slider.y+slider.radius)

        point(mouseX+i, mouseY+j);

    }

  }

}

​

function prob(dist){

    return exp(-(dist**2)/probConstant);

}

​

function onSlider(){

  return sqrt((mouseX - slider.x)**2 + (mouseY - slider.y)**2) < slider.radius + 5;

}

​

function dragSlider(){

  dragMode = true;

  slider.x = mouseX>30 ? (mouseX<windowWidth-30? mouseX : windowWidth-30) : 30;

  probConstant = (slider.x-30)*1024/windowWidth;

}

​

function mouseReleased(){

  dragMode = false;

}