​

function setup() {

  createCanvas(400, 400);

}

​

function draw() {

  background(220);

​

  if (mode == 0) {

    screen1();

  } else if (mode == 1) {

    screen2();

  } else if (mode == 2) {

    screen3();

  }

}

​

//Useful to have multiple elements on one screen

function screen1() {

  ellipse(width / 2, height / 2, 300, 300);

}

​

function screen2() {

  rect(50, 50, 300, 300);

}

​

function screen3() {

  line(0, 0, width, height);

  line(0, width, width, 0);

}

​

​

// //Method 1: More flexible, any order

// function mousePressed() {

//   if (mode == 0) {

//     mode = 1;

//   } else if (mode == 1) {

//     mode = 2;

//   } else if (mode == 2) {

//     mode = 0;

//   }

// }

​

// Method 2: Can only go in order

function mousePressed(){

  mode=mode+1;

  if (mode==3) {

    mode=0;

  }

  print(mode);

}