let c = color(str)

  c.setAlpha(alpha * 255)

  return c

}

​

let temp = 72

const freeze = 32

const boil = 212

​

function setup() {

  createCanvas(200, 200);

  textAlign(CENTER)

  rectMode(CENTER)

  noStroke()

}

​

function draw(){

  background(255)

​

  fill(80)

  square(50, 50, 100)

  square(150, 150, 100)

  let circleAlpha = map(temp, freeze, boil, 0.0, 1.0)

  let circleColor = fadeColor('lightskyblue', circleAlpha)

  fill(circleColor)

  circle(100, 100, 120)

  fill(0)

  text(temp, 15, 190)

  temp += 2

  if (temp > boil){

    temp = freeze

  }

}