let g = 0;

let b = 0;

​

function setup() {

  createCanvas(400, 400);

}

​

function draw() {

  background(255);

​

  fill(r, g, b);

  textSize(183);

  text("a", 150, 150 + 99);

​

  noFill();

  noStroke();

  rect(150, 150, 100, 100);

​

  if (mouseX >= 150 && mouseX <= 150 + 100 && mouseY >= 150 && mouseY <= 150 + 100) {

    //if we've rolled over do something

    r = 255;

    g = 150;

    b = 0;

  } else {

    r = 0;

    g = 0;

    b = 0;

  }

​

}