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For the impatient: how to start it all

In your terminal, type:

$ cd engine
$ make
$ make start

Then, open the following url in your browser


Finally, click on the start simulation button. Enjoy!


A tale of blah blah blah aims at being a simulation of a real world (oh, well...) where inhabitants are carrots, rabbits and wolves. In this world, the following things can happen:

Rabbits can eat carrots.
Wolves can eat rabbits.
Carrots... stay still and wait to be eaten.


Wolves can form *wolves pack** and chase rabbits!*

Our main goal has been to

  • model the world
  • play with the world params and try to make it lasts as long as possible, i.e. try to avoid the immediate extinction of all the species

Note: Since we didn't find a graphic character for the wolf, we replaced him with the infamous tac nayn [1]!


No surprise, carrots, rabbits and wolves have been implemented by means of finite state machines. The hard part -- of course -- was to synchronize the processes together, avoiding inconsistent states of the application.

The moving behaviour of carrots and wolves has been implemented in the kinematics module, which exports the following functions:

wander/2  %% wandering
seek/2    %% once a rabbit has seen a carrot nearby, try to approach it
flee/2    %% once a rabbit has seen a wolf nearby, run away!
pursue/2  %% once a wolf has seen a rabbit nearby, chase it!

At each moving step, both wolves and rabbits lose a bit of their health. If they are able to eat something, their health level will raise. If they don't eat for a long time, they will die.

Every time a carrot is eaten, a new carrot is spawned and added to the world, keeping the number of carrots constant.

Finally, the wolf pack behaviour, has been implemented by the experimental pg module: when a wolf sees a rabbit close to him, it immediately notifies his fellows calling

pg:esend(wolves, {chase_that_rabbit, R})

All wandering wolves will immediately chase that rabbit.

The user interface, that is, the html page that you opened before in your browser, contains an HTML5 canvas, which at every game step by a javascript controller.

To get the world status, we query the game engine using websockets. The game engine makes use of cowboy to handle the request, collects the state of the world, then gives it back in JSON format.


Loris Fichera
Mirko Bonadei
Paolo D'Incau


Here in Italy we have the concept of zona Cesarini, which means in extremis.
Well, it was mid June and we were, still, without ideas for the spawnfest.
Suddenly, a nice thought came up to Mirko's mind... he remembered of a curious exercise that Francesco Cesarini did when he was a student in Uppsala University [2]. We can make something similar!, we thought.
Well, this has been our zona Cesarini, for real. :)

What else?

There are a lot of things in order to make A tale of blah blah blah a better software.

But, hey, spawnfest it's just 48 hours and... we have been working from three different places (one of us has been even travelling for work while doing the spawnfest) and, last but not least, we never met in person before the spawnfest. Being able to take part to the spawnfest and submit something is our little victory. :)

Going onto practical ground, the following things could be implemented/improved:

  • actors must not go outside of the playing field
  • kinematics can be improved: sometimes movements are not too... intelligent :)
  • implement spawn of new rabbits/wolves when their health level goes over a certain threshold
  • let the user choose the parameters from the html page
  • refactor env_manager and use ets instead of lists to store the game status
  • names harmonization



Other Resources

All of the artworks used in this project has been found on internet and are free to use. Sadly, time is running out. Once spawnfest is over, we will open the repository and update this readme, giving credits to the brave designers who, unintentionally, helped us. :)