Learning Through Tinkering

As presented @ fooConf

All the references I made in the presentation are in this post, as well as links to some code repositories to get you started!


Slides available as PDF

Technical Content

Game Engine (update/draw-loop)

For the game engine I followed a blog from James Cho. It is an amazing step-by-step guide to build a game engine in Android. It’s quite easy to change that Android implementation into JavaFX! The tutorial is getting quite old but I had no problem following it and reaching my goal.

While his entire website is full of info, I specifically used these pages:

Game Physics

You can only model something correctly if you understand it to the fullest. While I had little understanding of physics there is an amazing resource available for free.

The Nature of Code by Daniel Shiffman is an amazing book which explains both the physics and how to program them in a simple way. I am still baffled by how simple he made it look.

    Abstract class used for most of the items on screen.
    This is what it looks like when only applying chapter 1 and beginning of chapter 2
public abstract class Drawable {
    protected Vector2 location;
    protected Vector2 velocity;
    protected Vector2 acceleration;

    public Drawable(Vector2 location) {
        this.location = location;
        this.velocity = new Vector2(0, 0);
        this.acceleration = new Vector2(0, 0);

    public void applyForce(Vector2 force) {

    public void update() {

        //Revert to 0

The best part is that he published his book in html format with Javascript examples on the internet. You can find it here: https://natureofcode.com/book/

The little Portal based game can be found here.

Attendance List

For the actual recognition, I just use Azure Cognitive Services Face API. It is extremely easy to use. Ask a free Azure trial and get going! :-).

As a buffer between the camera (a stream of images) and the Face API (a single request/response frame) I employed OpenCV. The most important part of the code is the following:

public void run() {
        // Select a Camera
        VideoCapture camera = new VideoCapture(0);

        // Load a Classifier (pre-trained model packaged with OpenCV)
        CascadeClassifier faceDetector =

        Mat frame = new Mat();
        // LOOP FOREVER!!!
        while (true) {
            if (camera.read(frame)) {

                // Run a detection on the frame
                MatOfRect faceDetections = new MatOfRect();
                faceDetector.detectMultiScale(frame, faceDetections);
                Rect[] detectedFaces = faceDetections.toArray();

                // Draw rectangles on the original frame
                drawRectangles(detectedFaces, frame);

                // only send the frame to Cognitive Services if you actually detected a face
                if(detectedFaces.length > 0) {

                // Render the edited frame in a simple application

The Github code example is here. I still need to clean the Repo a bit.

Lessons Learned from Pokemon Go

  • They do not use JSON to communicate, they use Google Protocol Buffers An example project with Protocol Buffers Maven Plugin can be found here

  • They use S2 Geometry which is a really cool way to index the earth!

The Plushy Stuff!

I wrote a blog about creating the “plushy controlled game”, going into the details of the solution:

Session Q&A

Here are some of the questions I was asked after the talk. Writing it down so you might benefit from it.

How do you remember to take a step back and reflect on what you are doing (to keep your goals clear in sight)?

One technique you might use is the “Pomodoro”-technique. In short, you set a timer for 25 minutes (you can choose your interval) and work until the timer rings. When time is up, you need to let go of your keyboard and relax a short bit. Before you start the next interval, that is a great moment to check if you are still on the correct path.

More about the “Pomodoro”-technique can be found at wikipedia. A free online time can be found at https://pomofocus.io/.

Do you have some advice for Team Leads on how to support their team in learning?

  • Psychological safety is important! You want your team to speak up when they get stuck or when a task is too far out of their comfort zone;
  • Get to know your team members weak spots/preferences. Keep the Zone of Proximal Development (circles!) in mind when giving them task;
  • Do pair programming or mob programming to really get to know your team members quickly! Guide them through the parts they find difficult and encourage an environment where knowledge is shared!

Where can I learn more about learning and self-ownership… any books you can recommend?

  • The Programmers Brain - Felienne Hermans: About cognition and how it impacts programming;
  • Thinking, Fast and Slow - Daniel Kahneman: More about the brain, biases and learning;
  • 7 Habits of Highly Effective People - Stephen Covey: About Self-ownership.
  • Atomic Habits - James Clear: Building habits to drive your personal life and career.