let eyeY = 200;  // Y position of the eye

let eyeSize = 100;  // diameter of the eye

let irisSize = 50;  // diameter of the iris

let pupilSize = 25;  // diameter of the pupil

​

function setup() {

  createCanvas(400, 400);

  background("#FF2E3F");

  angleMode(DEGREES);

}

​

function draw() {

  background("#FF2E3F");

  drawEye(eyeX, eyeY, eyeSize, irisSize, pupilSize);

}

​

function drawEye(x, y, eyeSize, irisSize, pupilSize) {

  // draw the sclera

  noStroke();

  fill("#F2F2F2");

  ellipse(x, y, eyeSize, eyeSize);

​

  // calculate the angle between the mouse position and the eye center

  let angle = atan2(mouseY - y, mouseX - x);

​

  // set a maximum distance the iris and pupil center can move (within the edge of sclera)

  let maxDist = (eyeSize / 2) - (pupilSize / 2);

​

  // calculate the distance between the mouse position and the eye center

  let distanceFromCenter = dist(mouseX, mouseY, x, y);

​

  // restrain the distance iris and pupil move so they stay inside the eye boundary

  let moveDist = min(distanceFromCenter, maxDist);

​

  // calculate the new iris and pupil positions along the angle

  let irisX = x + cos(angle) * moveDist;

  let irisY = y + sin(angle) * moveDist;

​

  // determine if the mouse is near the edge or outside the eye

  let edgeThreshold = (eyeSize / 2) - irisSize;

  let stretch;

​

  // apply stretch factor when near the edge or outside the eye

  if (distanceFromCenter >= edgeThreshold) {

    stretch = map(distanceFromCenter, edgeThreshold, eyeSize / 2, 1, 0.5);

  } else {

    // no stretch inside the inner part of the eye

    stretch = 1;

  }

  // constrain stretch between 0.5 and 1

  stretch = constrain(stretch, 0.5, 1);

​

  // draw the blue iris with dynamic stretch

  push();

  translate(irisX, irisY);  // move to iris position

  rotate(angle);  // rotate based on the angle to the mouse

  fill("#275AF2");

  ellipse(0, 0, irisSize * stretch, irisSize);

​

  // draw the black pupil with dynamic stretch

  fill(0);

  ellipse(0, 0, pupilSize * stretch, pupilSize);

  pop();

}