let num1;

let num2;

let sum;

​

function setup() {

  createCanvas(400, 400);

  textFont("Source Code Pro");

  textSize(20);

}

​

function draw() {

  background(250)

  add(66, 66);

  show();

}

​

function add(num1, num2) {

  sum = num1 + num2;

}

​

function show() {

  text("66+66=" + sum, 100, 100)

}

//want to do something fancy, but failed 

/*function draw() {

  background(220);

  print(this.num1,this.num2);

  show();

​

}

 function add (mouseIsPressed) { 

   this.num1=random (20,60);

   this.num2=random (40,90);

   this.sum=this.num1+this.num2;

  }

​

function show () {

  text("=", 100,100);

  text(this.sum, 103,100);

}

*/