let largeSize = 200;

let currentSize = 0;

let destinationSize = smallSize;

​

function setup() {

  createCanvas(400, 400);

}

​

function draw() {

  background(220);

  // see if the mouse is less than the radius of the circle

  // that means it's inside the circle

  if (dist(mouseX, mouseY, width / 2, height / 2) < currentSize / 2) {

    destinationSize = largeSize;

  } else {

    destinationSize = smallSize;

  }

​

  // SMOOTHING

  // subtract where we are currently from where we want to be

  // then scale that down and add that number back into the current number

  currentSize += (destinationSize - currentSize) * 0.1;

​

  circle(width / 2, height / 2, currentSize);

}

​