let stay = false;

let lx;

​

function setup() {

  createCanvas(600, 600);

}

​

function draw() {

  background(20);

​

  for (lx = width / 3; lx <= width; lx += width / 3) {

    stroke(255);

    line(lx, 0, lx, height);

  }

​

  if (on) {

    noStroke();

    fill(200, 50, 150);

    rect(width * 2 / 3, 0, width / 3, height);

  } else {

    noStroke();

    noFill();

    rect(width * 2 / 3, 0, width / 3, height);

  }

​

  if (stay) {

    noStroke();

    fill(200, 50, 150);

    rect(width * 2 / 3, 0, width / 3, height);

  } else {

    noStroke();

    noFill();

    rect(width * 2 / 3, 0, width / 3, height);

  }

​

  if (mouseX > 2 * width / 3 && mouseX < width) {

    if (on) {

      stay = true;

    } else {

      stay = false;

    }

  }

  if (mouseX < width * 2 / 3) {

    on = false;

  }

}

​

​

function mousePressed() {

  if (mouseX > 2 * width / 3 && mouseX < width) {

    on = true;

  }

}