var teal = "#43b8b0";

var w,h;

​

function setup() {

  w = windowWidth;

  h = windowHeight;

  createCanvas(w, h);

  textFont("Fira Code");

  textSize(16);

}

​

function draw() {

  background(teal);

  noStroke();

  fill(0);

  text(`var size = ${size|0};`, 15, 30);

  noStroke();

  // we use "size" to fill the color also

  fill(size);

  circle(windowWidth/2, windowHeight/2, size);

  size = map(constrain(mouseY, 10, height), 10, height, 0, 255);

}

function windowResized() {

     resizeCanvas(w, h);

  };