Whistle Your Way Through A Cave in: Hyper Bat Simulator 2018!

A few weeks ago was the end of January, and many game developers know what that means: It’s time for yet another Global Game Jam! The GGJ is a world-wide event with hundreds of locations where people meet for 48 hours of rapid game development.

This year’s theme was “Waves”, and I found myself with a team that I’ve never worked with before – which is always challenging, but also fun! The development went nearly without any hitches and I’m really content with our result:

In the game, you are a bat flying through a cave looking through the bat pups so you can go hunting. The cave is dark and the pups are tiny, so you use your echolocation to see and hope the pups answer. You steer with the gamepad – but to use the echolocation, you have to whistle into a microphone! (Like the title suggests, this is definitely the latest in bat simulation technology.)

Here’s a video of our presentation after the GGJ (starts at 0:29):

Global Game Jam Berlin 2017 Presentations – Bat Simulator 2018


And a small trailer video Emily and Caroline made:

Hyper Bat Simulator 2018


The game and its source code is available at its Global Game Jam entry page.

Before I talk a little more about the development, here’s the team:

We also used some assets:

Okay, on to the development! This time (and very atypical for me), the concept was rather simple. A single player game with no really hard development challenges – well, that leaves more room for polish, and sounds just right for 48 hours!

This was also one of the few times where the game design didn’t change much over the course of the weekend. Everything just worked. In the end, we actually finished the game with all the features we wanted! We even removed some features we already implemented because they made the game less accessible and weren’t as much fun as we had imagined: Dizzyness when the bat crashed into a wall, and not being able to call out to children when there’s a wall in the way. We also wanted to add monsters that follow sound, but in the end the game turned out to be plenty fun without the added complications, so we decided not to go that route.

The microphone implementation was incredibly easy, more so because this isn’t my first microphone controlled game. I just had to sample the input volume and detects peaks.

First I wanted to do the echolocation waves via shaders, but that that would’ve taken some time. Then I remembered something I learnt about in a Pluralsight video tutorial just a few weeks ago: Light Cookies, which allow you to put shadow masks on Unity3D lights. The final echolocation waves are just multiple spotlights with a circular light cookie mask shining from above, and the angle gets progressively bigger. That way it “runs” across obstacles and scales walls and stalagmites instead of just looking like it’s two-dimensional shape projected from above. The effect is a bit hard to describe, but you can see it quite often in the videos linked above.

I am really happy with our result! Thanks a lot to my team for being the best team – and to the location organizers and the Global Game Jam team who made it possible for us to jam without worrying too much about such mundane things as work space or food!

KinectMagic – A Kinect Wizard Duel Game Prototype

In my studies at the HTW Berlin, I had a course called “Independent Coursework” where I could choose to work on any project relevant to my studies. I chose to work on a Kinect multiplayer game which should also be interesting to watch. Most important to me was that the game uses what the Kinect does best in my opinion: Spacial movement. I didn’t want any repetitive gestures, just a direct relationship between the players and their avatars. So, together with my fellow student Jana Leinweber I set out and developed, and a few months and a dozen iterations later we had this:


Create spells! Attack! Defend! Dodge!

Tactical spellcasting meets fast reflexes in this
duel game for two wizards and a Kinect v1.

Download for Windows

KinectMagic – A Kinect Wizard Duel Game Prototype

SnakeFormer: Half Snake, Half Platformer! (Post Ludum Dare Compo Edition)

A few months ago, I made my first puzzle game ever for Ludum Dare 29. It was well received (#16 in Innovation!) and players called it “clever” and “challenging”, but the difficulty curve was too steep. Now, I finally found the time to make a post-compo edition with more and easier tutorial levels to ease the beginning and a really hard one where you can test your mettle! I humbly present:


Snake meets platformer physics!

A short puzzle game combining two
well-known concepts to form a unique hybrid.

Play right here in your browser!
(And maybe rate it! Or share it with friends who might like it.)

Download for Windows, OS/X or Linux!

SnakeFormer – Half Snake, Half Platformer (Post Ludum Dare Compo Edition)

“But,” you might say, “only 9 levels?” Yeah, for now. I think it’s enough to demonstrate the concept well and especially the later levels might take some time to solve. I’m pondering releasing it on Android soon, and maybe, just maybe, I’ll search for a level designer and get more levels made. If you like it and want more of it, please leave a comment!





StarCoder: A Short Game Programming Workshop For Total Beginners

15 Minutes in the Shoes of a Game Programmer

For a workshop at the YOU, a youth culture fair, I was asked to make a concept for a short game programming workshop.

The requirements were:

  • The workshop should give an impression of the work of a game programmer.
  • It should take about 15 minutes and allow groups of varying size.
  • I should assume that the participants have no experience in programming at all.
  • Instructions should be kept to a minimum; the focus should be on hands-on experience.
  • The workshop should produce a quantifiable result.
  • It should be an enjoyable experience.

No easy task. Luckily, inspiration struck, and a few days later I finished the game StarCoder.


Move the player to the star by using
Left/Right and Space to jump.

An easy game if it weren’t for the spikes –
or if you could jump far enough, for that matter.
Luckily you can edit the source code.

There are 15 distinct solutions to win the game.
How many will you find?

Download for Windows

Source Code (License: CC BY SA)
Creative Commons License

StarCoder: A Short Introduction To Game Programming For Total Beginners

The Workshop

The workshop went extremely well. Everybody found at least 4 solutions, with some finding up to 10. The game also seems to be surprisingly fun, even (or especially?) for non-programmers! Results were often accompanied by laughter and some of the participants even asked for the program so they could try it again at home. And I remember a teacher who sat down to try it himself after I finished the workshop with his group of pupils.

If you use it yourself (which I’m totally fine with – I’d love if you drop me a message that you are using it!), this was my approach:

  • Tell your attendees that the goal of the game is to get to the star. Ask them to click in the left part and try it themselves: Arrows keys to run, Space to jump.
  • After half a minute admit that it seems rather impossible – but luckily there’s the source code on the right side which they may edit. Ask them to notify you once they have a solution.
  • Once they have the first solution, congratulate them for their achievement. Then ask them to click on “Reset” in the lower right corner and tell them that there are 14 more solutions.
  • After a few minutes (or a few solutions, depending on their speed), tell them that there’s also the “Creation” tab in the upper corner.

The ideal number of attendees seems to be 1 to 3 per computer. You might want them to write down their solutions if you want to assign a score to each group later.

So… how about you? Did you find every single one of the 15 solutions? Try it yourself first – and then check it with this handy walk-through. (No cheating though!)

And if you’re interested how hard solutions are and which are found the most and least easily, you can check out these statistics (contains spoilers!).


  • Concept, Programming and “Art”: Tobias Wehrum
  • Sounds: Moritz Ufer

Thanks to my playtesters: Moritz, Tobias, Kelvin, Sebastian, Simon, Christiaan, Lukas, Florian, Marina, Jana, Jens, Paul, Ronja and Nadine. You guys have been a huge help!

Made in cooperation with:

Hammertennis: Tennis, But With Giant Hammers Instead Of Rackets

Take Hammerfight. Add Pong. Mix and stir. Sprinkle with a little realism and Tron.

Recipe serves 2.


You are playing Tennis. Well, you’re trying to play Tennis.
You’ve lost your tennis rackets, so you take hammers instead.
Also you’ve forgotten most of the rules.

Hammertennis: A fast-paced ball game for 2 players.
Supports Keyboard – or Gamepads! (You only need one stick. Choose any.)

Download the Windows executable

Hammertennis Gameplay

You get 2 points for scoring a goal, and 1 point if the opponent hits his own goal.

Normally only the hammers can hit the ball – but if the ball is red, the blue player can hit it once, and vice versa.

This is the first game I ever started with Python, featuring Pygame and pybox2d. Lovely language! It is also the first game that I ever made that uses any serious form of physics.

Both are thanks to Florian Berger, who is teaching the university course that got me started on making a Python game featuring any form of physics in the first place. Thanks a lot, it was great fun and (obviously, see above) had great results!

You can also download the source code (New BSD License) if you like! It needs Python 2.7, pygame 1.9.1 and pybox2d 2.1.