What is this?

This started out as a blog for written answers to assignments from a course in Computer Game Design 1 at the Royal Institute of Technology (KTH) in Sweden. Its purpose is to serve as a diary of sorts. It is a place where I jot down ideas, thoughts and reflections about my life and computers.

It is solemnly written by me, Anton Erholt (twitter: @aerholt, github: @antonaut). I am 27 years old and live in Oslo, Norway. I am originally from Sweden, but moved here pretty recently. Currently I am working as a software engineer at Conax and finishing my master's thesis.

This blog is in chronological order, with the oldest post at bottom. Yes if you want to read it, you have to scroll. This may seem a bit old-fashioned, but it is just the way I like it. I have started using proper links as well and omitted the footnote style for the newer posts.

Dear reader, hopefully it will be to your liking.

Portfolio   portfolio

These are some of the projects I have been involved in, one way or another. Most of the projects are related to school, but some have I worked on during my free time.


Aerial is a project where you control an airplane by moving a smartphone around. The goal of the project was to make something which somebody paralyzed from the neck and downwards could interact with. The smartphone is supposed to be attached to your head and you control the plane by tilting your head back and forth or side to side.

I worked mostly on project management and fixing the issues we had, as well as some of the mathematical modeling needed.

This project was part of the KTH course AGI-15.

Figure 1: Gameplay of Aerial.


Padawan101 is a light saber simulator made for Oculus DK2, a Microsoft Kinect and a smart phone. The project was built with Unity. We combined a lot of technologies to get body and light saber tracking working correctly. Worked on a lot of stuff during the project. What I worked the most on was actually networking, to create even more views so that people could join and look at the jedi fighting. I was also responsible for the project web page.

Padawan 101 - project video from Viktor Leandersson on Vimeo.

The code is available here. This project was also part of the KTH course AGI-15.

Put put glorify!

Bm-putputglorify is a multiplayer game to be played on a big screen using smart phones as controllers. You spawn as a shell, the objective is to crash into other shells. Me and some of my friends built it as part of a 'pizza & javascript' - hackathon.

Figure 2: Gameplay of bm-putputglorify

Rendering with ray casting and rasterization

I built two renderers using ray tracing and rasterization as part of a introduction course to computer graphics.

Moves where a Queen can't take (8x8 chess board), Apr 17   code problem clash

;;; Finds okay positions where a single queen can't take the piece (8x8
;;; board) It sure took a while to write, but now it's sort of understandable
;;; and done in a functional style.
;; TOO SLOW! (1h 10min)

;; Learned about generation with lazy-seq and map-indexed together with
;; list comprehension (for).

;; Simulates input.
(def one-Q-board
  [["." "." "." "." "." "." "." "."]
   ["." "." "." "." "." "." "." "."]
   ["." "." "." "." "." "Q" "." "."]
   ["." "." "." "." "." "." "." "."]
   ["." "." "." "." "." "." "." "."]
   ["." "." "." "." "." "." "." "."]
   ["." "." "." "." "." "." "." "."]
   ["." "." "." "." "." "." "." "."]])

;; Will be used as a base board to build on.
(def all-p-board
  [["P" "P" "P" "P" "P" "P" "P" "P"]
   ["P" "P" "P" "P" "P" "P" "P" "P"]
   ["P" "P" "P" "P" "P" "P" "P" "P"]
   ["P" "P" "P" "P" "P" "P" "P" "P"]
   ["P" "P" "P" "P" "P" "P" "P" "P"]
   ["P" "P" "P" "P" "P" "P" "P" "P"]
   ["P" "P" "P" "P" "P" "P" "P" "P"]
   ["P" "P" "P" "P" "P" "P" "P" "P"]])

;; Direction functions for taking a step in the next direction.

(def dirs {:topleft   (fn [[x y]] [(dec x) (dec y)])
           :top       (fn [[x y]] [x (dec y)])
           :topright  (fn [[x y]] [(inc x) (dec y)])
           :left      (fn [[x y]] [(dec x) y])
           :right     (fn [[x y]] [(inc x) y])
           :downleft  (fn [[x y]] [(dec x) (inc y)])
           :down      (fn [[x y]] [x (inc y)])
           :downright (fn [[x y]] [(inc x) (inc y)])})

(defn outside-board?
  "Stop the lazyness with this when you fall off the board."
  [[x y]]
  (or (< x 0)
      (> x 7)
      (< y 0)
      (> y 7)))

(defn advance
  "Take a step forward."
  [dir pos]
  ((dir dirs) pos))

(defn advanced-positions
  "Lazily take several steps forward."
  [dir pos]
   (cons pos
         (advanced-positions dir (advance dir pos)))))

(defn take-positions
  "Find all the positions where a queen can take a piece."
  [[x y]]
  (for [dir (keys dirs)
        pos (take-while
             #(not (outside-board? %))
             (advanced-positions dir [x y]))]

(defn find-string-on-board
  [board string]
  (for [row   (map-indexed vector board)
        col   (map-indexed vector (second row))
        :when (= string (second col))]
    [(first row) (first col)]))

(defn find-queen [board]
  (find-string-on-board board "Q"))

;; Functions for updating a board / 2d-seq

(defn update-row [row x val]
  (map-indexed (fn [xidx col]
                 (if (= x xidx) val col)) row))

(defn update-board [board [x y] val]
  (map-indexed (fn [yidx row]
                 (if (= y yidx)
                   (update-row row x val)
                   row)) board))

;; (update-board one-Q-board [2 3] "X")

(defn ok-positions
  (let [qpos       (first (find-queen board))
        tpositions (take-positions qpos)]
     (map reverse
          (loop [tpositions tpositions
                 board      all-p-board]
            (if (empty? tpositions)
              (update-board board qpos "Q")
              (recur (rest tpositions)
                     (update-board board
                                   (first tpositions)

(ok-positions one-Q-board)

Results in:

(("P" "P" "P" "." "P" "." "P" ".")
 ("P" "P" "P" "P" "." "." "." "P")
 ("." "." "." "." "." "Q" "." ".")
 ("P" "P" "P" "P" "." "." "." "P")
 ("P" "P" "P" "." "P" "." "P" ".")
 ("P" "P" "." "P" "P" "." "P" "P")
 ("P" "." "P" "P" "P" "." "P" "P")
 ("." "P" "P" "P" "P" "." "P" "P"))

Spiral matrix in Clojure, Apr 15   code problem clash

I had a bit of a struggle with this problem at first. I decided to generate the path with a few small functions and then sort and print. Enjoy this beatiful piece!

;;; Prints numbers in a spiral matrix going ⟳.
(ns first.spiral)

(defn output-number [n]
  (if (< n 10)
    (str "0" n)
    (str n)))

(defn right [[x y]]
  [(inc x) y])

(defn left [[x y]]
  [(dec x) y])

(defn up [[x y]]
  [x (dec y)])

(defn down [[x y]]
  [x (inc y)])

(def dirs {:right right
           :up    up
           :down  down
           :left  left})

(def rotate {:right :down
             :down  :left
             :left  :up
             :up    :right})

(defn advance-dir
  (if (contains? visited ((current-dir dirs) pos))
    (current-dir rotate)

(defn spiral [W H]
  (let [stop (* W H)]
    (loop [pos            [1 1]
           next-dir       :right
           current-number 1
           visited        #{[(inc W) 1]
                            [W (inc H)]
                            [0 H]}
           matr           #{}]
      (if (= stop current-number)
        (conj matr [pos current-number])
        (recur ((next-dir dirs) pos)
               (advance-dir ((next-dir dirs) pos)
               (inc current-number)
               (conj visited pos)
               (conj matr [pos current-number]))))))

(defn cmp-pos [[[x1 y1] _]
               [[x2 y2] _]]
  (cond (< y1 y2) -1
        (> y1 y2) 1
        :else     (cond (< x1 x2) -1
                        (> x1 x2) 1
                        :else     0)))

(defn print-row
  (loop [row row]
    (if (= 1 (count row))
      (println (output-number (first row)))
        (print (output-number (first row)) " ")
        (recur (rest row))))))

(defn main
  "Width and height of matrix to be printed.
  Looks really bad if either of them > 9."
  [W H]
  (let [xs   (sort cmp-pos (spiral W H))
        mat  (partition W xs)
        rows (map #(map second %) mat)]
    (map print-row rows)))

;;(main 5 3)
(main 9 9)

Results in:

01  02  03  04  05  06  07  08  09
32  33  34  35  36  37  38  39  10
31  56  57  58  59  60  61  40  11
30  55  72  73  74  75  62  41  12
29  54  71  80  81  76  63  42  13
28  53  70  79  78  77  64  43  14
27  52  69  68  67  66  65  44  15
26  51  50  49  48  47  46  45  16
25  24  23  22  21  20  19  18  17

Improving my Clojure skills, Apr 15   code problem clash

Over at CodinGame they have something called clashes of code where you compete with other developers to solve a certain problem in a given amount of time. I know there are quite a few sites where you can sharpen your coding skills, but somehow I got stuck at this one. Maybe it provides me with just enough challenge for me with my current skills.

I've tried to use the clashes to learn more about Clojure. So far I've come to realize that there are a TON of functions I don't know of. I feel like I learn something new on (almost) every problem. Even though I can't finish most of them on time, I still try to complete them. I'll put some of my solutions to a few of the more interesting solutions here.

End of my game dev story? Apr 09   gamedevstory

We worked on this for a while, but it just ran out in the sand when I went to France for exchange studies. Nevertheless, it was a great learning experience for me. I think I mostly learned a bunch of javascript. We built the client side of a somewhat advanced game. The coolest part was a small window system built mostly by my friends in WebGL.

Hopefully we can publish the code with some small examples.

Sphere packing on a sphere? Circle packing papers, Mar 08   math topology

The idea of a tool giving you access to finding relevant papers in a certain field of research is pretty interesting. Let's imagine all the papers as a planar graph depicted on a sphere. The edges (arrows/links) of the graphs are keywords or subjects. A certain 'theme' (a set of papers) would then be a 'continent' on the sphere.

Figure 3: Found on a course web page for computational topology, originally from http://www.math.utk.edu/~kens/BookInfo.html. I should totally read that book.

Imagine this thing spinning and showing you the papers you've found, then expanding those with related papers - pushing the old papers aside. Found an example done in 2D with d3.js for dependencies https://bl.ocks.org/mbostock/7607535. Would it be interesting to see this in 3D? Maybe in an AR setting. The zooming effect would probably come naturally if the spheres grow to big. I sort of like the concept of several virtual globes for organizing stuff. Not so sure of how I would feel about them in reality though.

Tools for completing a master's thesis, Feb 25   thesis tools emacs

A master's thesis is an intense 18 weeks of total focus and devotion to a research question. So far, I've only been able to invest about one weeks worth of studies during a four week period. My personal life is taking its toll on my work at the moment. I don't feel like it's that frustrating, but I'd really like to get more stuff done.

In order to increase my productivity I've come up with a plan.

  1. Devote more time to planning in the morning
  2. Use a pomodoro (from Italian: means tomato) timer when working to minimize distractions

To keep track of my pomodoros, I use a simple app called Productivity Challenge Timer.

These two simple things should allow me to plan the process more smoothly.

Step one in the process of the thesis is to write a specification document. The document should provide detailed information of the following things:

  • The goals of the thesis, what I hope to achieve
    • Why it is important
    • To whom is it important
  • My own background and why I'm eligible to write it
  • The research question this thesis will try to explore and answer
  • A detailed timeplan for when everything should be done

Just like this blog, I'll largely write my thesis in emacs with org-mode. I've started to organize some of the references I've found in Mendeley Desktop and in an org-mode file. I also found a nice latex-package for doing gantt-charts called pgfgantt.

Concerning idea debt and investment, Feb 25   documentation ideas

I read this article about idea debt. Not sure which affected me the most. What she stated about idea investment, or the fact that she too doesn't know how to use the french subjunctive correctly. Nonetheless, I'm truly inspired to put my old ideas to the side and work with what I've got at the moment. I want to start documenting stuff properly. This is my blog. My life.

2016   newyear

Happy new year 2016!

2015 was not a very bloggy year. Who knows? Maybe 2016 will bear more blog fruit.

Regarding problems which can be solved by dynamic programming techniques, Jan 22   dynprog recursion bfs

I have recently watched quite a few videos on dynamic programming. What is dynamic programming? It's a method for constructing efficient solutions to some specific problems. In order to apply the method, there are some criteria needed to be met.

  • The problem should have a brute-force solution/exhaustive search solution.
  • The problem should be dividable into sub-problems with optimal solutions (explained further down)
  • The problem should have a recursive definition.

NOTE: I'm not doing this in a formal manner, I simply think out loud in order to understand the subject better.

Let's use these criteria to make up a problem which we could solve.

Definition of optimal

I'm thinking of the second criteria, that the problem should be dividable into sub-problems with optimal solutions. What do I mean by that? Well, being optimal means that if the original problem is split into parts, and you find a solution for a part, you know that the solution is the best possible solution for that part. Simple as that.

A recursive thought

You can use these "smaller" solutions to construct a "bigger" solution for the original problem. This is obviously a recursive thought.

  • "I start with a lot of small simple problems, and I use them to construct a bigger solution."

It is however a lot more common to state (or think about) recursion the other way around.

  • "In order to find a solution to this problem, I need to build it up from smaller solutions by dividing the problem into sub-problems. When the sub-problems become small enough, the solutions will be trivial."

The second statement is a lot longer when expressed in text, but when expressed with math, it becomes a lot more concise as well as more beautiful.

Brute force?

Well, this part I am not so sure about. Something in the back of my mind tells me that the problems in question should be solvable by performing some kind of exhaustive search (trying all variants of solutions which could possibly be generated) in a (what computer scientists would call a) non-efficient manner (referring to that it would take A LOT of time if the problem is big - usually exponential compared to the size of input).

Do you have a problem?

I think before I dwell any further into what the dynamic programming method is all about, I'd like to try and see if I can come up with a good problem. I've recently come to realize that constructing problems can be just as efficient as a learning tool as actually solving them. Conversation with myself follows:

  • A1: Let's pick a subject!
  • A2: Sports!
  • A1: Okay, what now… Where's the recursion?
  • A2: I'm thinking a football league… NO! Ice-hockey!
  • A1: Okay, keep going.
  • A2: Well, let's say there are 12 teams like in the Swedish Hockey League. They will all play against each other twice per season.

\(\mathbf{I}\): This would result in \(nPr(12,2) = 132\, matches\).

\(\mathbf{II}\): It could probably also be expressed like \(nCr(12,2)*2 = 132\).

In fact, \(\mathbf{I}\) is a special case of permutations when we only have two matches per season. It makes more sense to use \(\mathbf{II}\) if we for any reason would like to increase the number of matches per season. Hmm… Interesting!

  • A1: Enough with the combinatorics, go on!
  • A2: Okay, let's think of a property of the matches we can use. The first one I can think of is the total number of goals made per match.

That's enough. I'll continue this some other time…

2015   newyear

Happy new year 2015!

A flawed idea of the halting problem, Mar 16   programming computer science

The halting problem is fairly interesting even though someone (Alan Turing) some time ago (1936) has proved that it can not be solved by a general algorithm. It is undecidable. Despite the fact, today when I woke up I had an idea.

Let us use a FSM to describe the program. Think of it as a FSM with A LOT OF STATES. Almost as if it is an Infinite State Machine (which would not be of much use), but rather a very large FSM.

Program A

int main()
  int a;
  a = function(0, 0);
  return a;

int function(a, b)
        int a,b;
  a = 1;
  b = 2;

  return a == b ? 0 : function(a, b);

Consider this Program A. It is written in a very small subset of C which only handles:

  • integer assignment
  • ternary if statement based only on integer equality comparison
  • function call
  • function return
  • probably something else which I've forgotten

The idea is to convert these statements into a set of transitions \(\mathbf{T}\) between the set of states \(\mathbf{S}\).

For example, we take the integer assignment and turn it into corresponding 232 - 1 possible transitions from the current state (and one more for assigning the same value again).

The function call flattens out to whatever the function is supposed to do and turns into an assignment.

The equality check performs either a transition to the 'then' state or a transition to the 'false' state.

Et voilà! With a bit more convincing, we can build ourselves a FSM of the program. When looking at the State-Transition graph (STG) we simply need to perform a Breadth-First-Search of the graph in order to tell if the program can halt or not. Right?!?

WHAT ABOUT INFINITE RECURSION? Well, if we perform some kind of lazy check if we have already entered the function a lot of times with the same parameters, we should have already visited the states before the function call. Or I mean we should somehow flatten out the func… HANG ON! IS YOUR 'SUBSET OF C' UNIVERSALLY COMPUTABLE? Meh, universally computable? I havn't really thought about it `[insert ellipsis here]`


Well yes, I kind of do. I mean, the STG will be a lot smaller if you use uint8's instead. There might actually be something of use here, since a lot of programs don't use unlimited precision for absolutely everything. Perhaps there's a lot to gain if we use other types than simply a 32-bit integer (since that what the ints precision is on my machine).


I'm not listening to you… What if we remove infinite recursion and/or infinite loops. I mean the stack isn't infinitely large and we can always keep track of how much we have looped. Let's remove this annoying feature of the language instead and see what that does!

Sigh… Computer science can be tough. But this is what I love about it. The science part. Even though my idea is filled with flaws it might inspire other me and other people to look into new things. Someone reading this not knowing that much C may discover that you can list your arguments like I have done for 'function'. It might not be the 'Next Big Thing' but this way I feel that I may somehow contribute with a bit of knowledge, simply by letting my thoughts flow freely.

Even though I get turned down a lot by both my own and others CRITICISM, I really love how it may lead me somewhere else and take me into new orbits of reasoning. The criticism is the fuel of my science engine. For instance, now I do wonder if the 'small subset of C' I chose is universally computable (or at least if I could write a Fibonacci generator in it?). I think that science being tough is not a bad thing. It is exactly how it should be. The interesting thing here is how you choose to percieve it. I choose to see it as way of generating new insights.


UPDATE (2014-09-28): Realised it won't compile. Function definitions are supposed to be declared before they're used.

HACKATHON!   gamedevstory

A lot has happened since we started developing the game. Our initial goal was to do these tasks during the hackathon:

  • WebSockets and API
  • TouchEvents
  • GameLoop and GameStates

Afterwards, we now have a somewhat working APICallSystem with Secure WebSockets. Unfortunately havn't our exportation framework for Android and iOS supported the wss protocol yet, but it'll hopefully be up and running soon. During the hackathon I had a great time. We put up a stream at Twitch.tv to stream everything while making tacos and listening to jazz from a jar (using something similar to this).

To use DDD or not (| !) to use DDD   gamedevstory

My initial thoughts on Data Driven Development was that it to some extent might have been unneccessary (mainly due to the fact that I didn't understand it fully). I thought that when making a smaller game, you probably wouldn't benefit from using a DDD code style at all. However, after reading this post on why one should use an entity-component-system composition of a game/gameengine, I have changed my mind.

Our initial approach to writing the game was with OOP (Object-Oriented Principles) which gave us a massive Character class, which as of right now only seems unneccessary. At the moment, the entity-relation software model seems like a great way for us to develop, since it will give us the benefit of partitioning almost everything into tiny beautiful pieces which almost magically works together.

As of right now we have a lot of coding to do in order to get our game playable (which of course is our current goal). Hopefully we'll be able to show off something soon.

The beginning of Anton's Game Dev Story, Jan 7   gamedevstory

About a year ago, me and two classmates (johntu & dmol) participated in a programming competition called Escape from /dev/null. The competition is based around having to program something that assembles a client to a web-based API revolving different things. The API gets further uncovered as you get further into the competition. It's a game in a game. Very meta and Oh-So-Lovely™ if you are into these kinds of things.

Back to the contest! As young and somewhat novice web programmers, little did we know what to expect as we entered the contest. Not entirely without effort, we smacked our heads together, right down in the free pizza, chunked it down hard with some delicious beer and ended up at somewhere in the order of second to last.

Figure 4: Our client for the space themed /dev/null

Needless to say, time passed and we participated in a few more similar contests. The game we are building is in fact a client for this particular game. Peter Svensson (@psvensson) has made a fabulous job of writing the game mechanics and providing it as a web service for us to write a client from. We use web technologies in the core and hope to deliver an exclusive fullscreen, WebGL experience to all of our players. Are you getting excited? No? Then, maybe a bit interested? Aha… You continue reading because of pity and self-recognition? Ah well, just wait until I tell you what the game is about…

2014   newyear

Happy new year 2014!

Presentation of game demo, Dec 13   game design

We made a presentation of a game demo we developed during the course 1. Here follows the script and some comments of the final presentation (NOTE: This might be a tedious read since… Well. You have been warned).

Presentation Script

Welcome Hi everyone and welcome to this presentation. We’re the group “Fat ninja” a.k.a. Kitten with Mittens. We are here to present a charming puzzle game with…


…an adorable Kitten. But is it so cute after all? Kitten with Mittens is a game where you lead Cat through a series of levels by using his moving abilities. The levels are puzzles where you need to think and plan your route beforehand if you want to complete the level successfully.

As you probably can tell by our awesome posters, the game is currently available on Android and iOS platforms, but today we will be demoing on the Windows platform (Microsoft Surface tablet) and a smart phone. Without spoiling anything more about the game, we are going to present a story to you.


In a warm and cozy house, far up in icy and cold Sweden, lives Cat the clumsy kitten.

One early winter morning, Cat is lying in a warm bed under a blanket. Sleeping and dreaming of catnip with not a single thought of ever going up.

  • “Aaaah, this will be a lovely day of doing nothing.”

All of a sudden, Cat feels the need to scratch behind the ear. As Cat moves the paw back-and forth on the head, Cat tries to unfold a claw for that extra bit of OOMPH in the scratch. Cat feels that all of the fingers are completely restrained and Cat can’t unfold them at all. What is this?! Cat panics and tumbles over, whelps the bed over and lands in an otherwise yummilicious bowl of morning milk.

Cat slowly lift the eyelids and discovers a pair of mittens on top of the paws. As if that wasn’t enough, already having the morning ruined by a non-scratched itch and immobilization of paws, Cat also discovers a long scarf tied way too hard around the neck. What used to be a warm kitty, soft kitty, little ball of fur - is now unhappy kitty, awake and wet kitty, no purr, purr, purr!

Will you help Cat rid the mittens?

Game play Showed a short video of actual gameplay

So what does the game play look like? All-in-all you can move the cat around by swiping left or right, jump by tapping and swing by pressing and holding when near a swinging platform. These abilities can be combined in order to create mind blowing and dazzling puzzles.

Art Original art hand-made by Kajsa. The cat is modeled and animated by Veronica in Blender.

Project plan On time.

Trailer, Thanks & Questions

Comments About the Game

Positive Feedback

The first thing that struck people was how cute and pleasing to the eyes the game was, even though it was not the most technically advanced game presented during the seminar. The prototype was completely made up from primitives that was at our disposal in Unity, a self made model (the cat) from Blender and watercolour made paintings that had been scanned in for the textures in the background as well as the textures on walls and the ground. They really liked the art direction as well and thought that the whole presentation (textures, level design and models) looked consistent as a whole.

The consensus about the game mechanics and level progression itself from the people who tried it was that it was addicting, since the reward of clearing a stage made you want to play the game for longer. They liked the rope mechanic too even though it is hard to master.

Another thing that people really liked was the original oral presentation that we made and the posters that we had put up on the walls in the seminar room. It definitely raised interest in our product, so from a managerial point of view it was a successful game announcement. Finally we got some nice comments from one of the persons from Swedish Game Awards who thought that we definitely should participate in their event. One of his comments were that he did not get as frustrated as he could have been when he failed to complete one of our hard levels. He said it was because you can never count on a kitten to behave as you want it to. We think it is a good comment, since it is hard to say the same thing about another game.

Constructive Criticism

The prototype levels got very hard a little bit too fast. This is due to us trying to cram in the rope functionality in an early stage, which is a hard technique to master. Especially if the player is not completely familiar with the rest of the control scheme.

People thought that the game was hard and frustrating at times due to too few descriptions of the controls. However, that was something that we were already aware of, but due to time constraints we did not have enough time to implement as many “tutorial elements” in the prototype version of the game as we would have liked.

Mobile games, Dec 6   game design

When playing a game on a mobile device, you have very little time to make the player interested. This is a very similar problem to the one where websites have only a few seconds to present the right content to the visitor or else the visitor will browse away from the site. These problems are hard to solve (their respective decision problems are probably way more than NP-complete [Comp. Sci. humor] ).

I don't believe for a second that there is an ultimate answer to how to keep players stuck in the game. One idea is to allow them to leave and then force them to come back. If you develop for mobile, it can probably be a good thing. To enforce the player out of the game wanting to play more. The player will then return later, eager to face new challenges for a while. Games which operates in this manner are Quizkampen, Wordfeud and Candy Crush Saga. I'd say that it is probably a good concept to incorporate in a mobile game.

If you focus on the specific part of just getting the player hooked, I would say that a good idea is probably to try to give the player a feeling of greatness. In one of my favorite mobile games, Stardash 2 by OrangePixel, you probably manage to clear two levels in under 30 seconds. You feel that it was pretty easy, but not too easy so you keep playing. Making the first few levels good are essential if you want players to stay in game.

In order to really strengthen the inferred feeling of greatness, it would be good to perhaps infer an achievement system. Perhaps an achievement for the first death is a good idea so it actually turns into something positive?

The game producer - Game business models, Dec 3   game design

Now I'll briefly discuss some business models. Please note that I'm probably a bit biased.

Pay-to-play (P2P)

The "standard" model. You pay for a game once and then it is yours. For all eternity… Oh, you want an example? Hmm… Let's see. Oh! Project Zomboid 3 mentioned in an earlier post is a good example.

  • Pros
    • You don't have to keep track of all the players
  • Cons
    • The eventual income will spike and then drastically fall.
    • Typically means there will be sequels if the devs are successful.


Well, the most obvious example I can come up with is World of Warcraft 4, where you pay a fee each month to continue playing.

  • Pros
    • Continuous cashflow means an ability to have continuous development
    • Makes scalability easier
  • Cons
    • Player database needed to keep track of payments etc.
  • Comments
    • I think this model is perfectly suited for the MMO type of games which take a lot of time and effort to maintain and develop. You already do have a player database with accounts, so this should not be that much of a problem.

Free-to-play (F2P)

A great example is the giant in the MOBA-genre 5, DotA 2. In this game you can buy skins and new visual styles for the characters in the game.

  • Pros
    • Players get to play, haters get to hate and lovers get to love. You don't have to feel bad for trying to trick money out of someone…
  • Cons
    • … or yes you do. But how!? This business model requires something else to generate income, such as ads or in-game purchases.

A thing to keep in mind is that it is not completely impossible to switch business model, even though it might hurt some of your playerbase. One example of where a switching between business models has been successful is Heroes of Newerth 6. The game is F2P since the 20th of July 2012 7 (is used to be P2P).

Dataspelsbranschen: the trade organization, Nov 29   game design

Today we had a guest lecture from Per Strömbäck of Dataspelsbranchen, the trade organization for Swedish game development. He wanted us to discuss two specific questions which all in all are quite important when it comes.

How can the game developer interact with the audience?

There are multiple ways of interacting with your target audience as a game dev. The easiest to come up with are probably through public forums, a wiki, social media and/or some other kind of web based communcation. However, I think the most important interaction comes from other settings though.

Perhaps you perform some usability tests on your game, meaning you pick some testers and perform interviews of them. Perhaps you play the game together with them and communicate through the game you have made? Perhaps your dev studio attends fairs or arranges workshops of different kinds (hackathons?), where you need to physically interact with players etc.

Usually when it comes to games, there is always a lot of feelings involved. Therefore I think it is really important to be honest with what goals you have with the game and what purpose it has. Otherwise you might end up having a really let-down playerbase since you introduced PvP in starting towns and did not discuss it with your player. Sure it is your game since you made it, but don't you have some kind of responsibility towards your playerbase?

Why does not in-game ads work?

I think In-game ads don't work because the amount of time a player spends in a game is minimal. At least when it comes to mobile games. I do think in-app purchases are a lot better. At least if they are done in a good way.

British technology magazine Wired has released an article on in-app purchases in Plants-vs-Zombies 2 8. The article explains extremly well how I think in-app purchases shouldn't work. I do not think that in-app purchases should give the player any advantages compared to when not having done them. I usually end up quitting these games immediately since they ultimately favor the player with the largest wallet. Which is insane.

Short on game physics and animation, Nov 26   game design

Some games are really nothing but great combination of physics, animation and astonishing scenery. One example I would like to discuss is a game called flower 9 (note, no capital f). In flower one controls a single petal flying in the wind over an enormous field. As you fly across the field, if you hit other flowers, some of its petals will join you in your flight. In order to complete a level you need to collect a certain number of petals and reach the end (although I don't think it is specified how many you need).

The game per se has not the intentions of being difficult or puzzly but rather to give the player a joyful experience. The game does not contain any dialogs or any specific interfaces. You simply control the wind (and thereby the petals) with your chosen controller.

In flower, I think the developers (Thatgamecompany) have made a great effort of using flow dynamics and beautiful scenery in order to make the game into what it is. This is a great use of flow physics and I'm really happy to see that games like these makes it onto consoles and do not just stay in the swamp of indie PC games.

Lastly, I'd like to say that there are times when you find out things which give you an advantage in the game due to physics being used in a "clever" way (some might argue glitchy or cheaty). I have currently got two good examples of this. The first one is very well known but still very funny. In The Elder Scrolls V: Skyrim, you can climb almost any mountain when riding a horse (as opposed to when you are not riding). I remember someone making a funny picture out of it:

View post on imgur.com

My second example is from a 2D platformer called Cave Story 10.

NOTE: Might contain some spoilers

Cave Story is a free action adventure independently developed by Daisuke Amaya (a.k.a. Pixel -> Pixel Studios). Originally released in December 2004 for PC, an upgraded version (Cave Story+) was released on Steam and it was later ported to the Nintendo 3DS by Nicalis. You play a robot called Quote (or Mr. Traveler) which you guide through the world.

Depending on the path you take, you may come across a machine gun. Leveling up said gun will make it more powerful and thus make more damage and a greater recoil. Without prior knowledge, the undersigned happened to find out by mistake that firing the machine gun downwards allowed for continuous hovering/floating. This made certain areas of the game a breeze to play through. Delightful, amusing and totally unexpected.

Using a game engine or building your own? Nov 22   game design

This post will be filled with spontaneous questions and answers related to whether one should use an existing game engine or create one from scratch.

What budget are you on? If I'm really low on a budget I'll probably use an engine if it can save me some time, since we all know; Time is money. The time saving aspect is also present when it comes to maintaining the game and/or improving it. It is important that the engine gives you a good workflow so you can easily work with it. A good idea might be to implement some simple games/demos/ideas in the few engines you are interested of and see which ever suits you the best.

Are you lacking a feature in the engine? You can probably extend the engine if it doesn't have all the features you require for a game project. Also remember that there are several other engines to choose from which might give you more features for free. This is obviously something you should consider when you make the actual choice.

What platforms should we target? Different engines allow us to target different platforms. This is obviously an important choice to make as well. It is kind of connected to the monetization issue. Do more platforms equal more profit?

So, Anton since you're into web apps. What about them?

Well, I personally really like the web, but I am not sure it is well suited for everyone. John Carmack mentions in a keynote from QuakeCon that he does not really believe in using javascript for high performant graphics in the browser 11. I am thinking that means it would be hard to get a triple-A title running as smooth in the browser as it does natively. However a lot of "smaller" games run perfectly in the browser with great graphics. I remember specifically when Supergiant Games released Bastion 12 on the Chrome Web Store. Beautiful.

The Sims - a short presentation, Nov 20   game design

We made a short presentation on the Sims in class. Here are the slides and the script.


  • The Sims is the first game in the series. Developed by Maxis and published by Electronic Arts, it was released for Microsoft Windows in February 2000.
  • The Sims 2 are released on September 14, 2004. The sequel, developed by Maxis, takes place in a full 3D environment with every sim having an aspiration system.
  • The Sims 3 are released on June 2, 2009. Game has open, seamless neighbourhood, with improved tools for sim creation, enhanced build and buy mode functions, and the introduction of wishes and goals.
  • The Sims 4 will be available in 2014. It allows creating sims with intelligence and emotion. It provides new intuitive creative tools to sculpt sims and build unique homes. Game gives control over the mind, body, and heart of sims to bring stories to life.
  • The Sims Online, The Sims Stories, MySims, The Sims Carnival, The Sims Medieval, The Sims Social …

HISTORY - Script/notes

  • Sims 1 - Seven expansion packs and two bonafide deluxe editions with exclusive content have been released for this game. By March 22, 2002, The Sims had sold more than 2 million copies worldwide, making it the best-selling P.C. game in history
  • The Sims 2 is set some 25 years after the original game. For instance, the Goth family has aged significantly with Bella Goth mysteriously vanishing in the 25-year period. Because the entire game has progressed from 2D sprites to 3D models, all content in The Sims 2 had to be created from the ground up. Electronic Arts has released eight expansion packs and nine stuff packs for The Sims 2. Over 400 exclusive items have also been released for this game via The Sims 2 Store
  • The Sims 3 sold 1.4 million copies in the first week, making it the largest release in PC gaming history at the time. The game has sold over 10 million copies worldwide since its release. Eleven expansion packs and nine stuff packs have been released for the third generation of the series. Notably, Maxis was no longer involved in the production
  • The Sims 4 is built upon an entirely new technology. The content from The Sims 3 will not be transferable to The Sims 4. The Sims 4 will be available for PC.


  • The Sims is one of first full-commercial strategic life-simulation video games that still is most successful artificial life game
  • Inspired other games
  • Has real life applications

EFFECTS OF THE GAME - Script/notes

Artificial life games and life simulations find their origins in artificial life research, including Conway's Game of Life from 1970. But one of the first commercially viable artificial life games was Little Computer People in 1985, a Commodore 64 game that allowed players to type requests to characters living in a virtual house. The game is cited as a little-known forerunner of virtual-life simulator games to follow. One of the earliest dating sims, Tenshitachi no gogo, was released for the 16-bit NEC PC-9801 computer that same year, though dating sim elements can be found in Sega's earlier Girl's Garden in 1984. In 1986, the early biological simulation game Bird Week was released. In the mid-1990s, as artificial intelligence programming improved, true AI virtual pets such as Petz and Tamagotchi began to appear. Around the same time, Creatures became "the first full-blown commercial entertainment application of Artificial Life and genetic algorithms".


  • Cheats - Infinite money - Maximum skills
  • Different objectives
    • Dream house
    • Killing
    • Woo Hoo
  • Aspects of life (University, Seasons, Pets…)


What’s the most memorable thing about the Sims? We think it depends greatly on how the player has behaved when playing. What do we remember the most? The cheats and the ability to play God. There are a lot of different cheats, and most of you remember ‘motherlode’ or ‘rosebud’ to get more money;!;!;!; We all have different objectives when playing the Sims such as acting out your dream of becoming an architect and designing your dream house, or perhaps playing God and killing your Sims off in different ways. There are several ways of doing this, like trapping your Sims in a room with fire, removing the ladder when they’re in the pool so they drown or simply by letting them age. Another way of behaving in game, could of course be to do “the right thing” and let their Sims create a family and live their life as intended. Also are several different aspects of life which the player can focus on, for instance “University, Seasons, Pets… etc.”

Future of procedural generation of content, Nov 19   game design

I really think that map generation or procedural content generation is something which is becoming more and more common in games. Instead of playing linear, story based games we get to experience multidimensional games where we create our own unique worlds (or have our own worlds created for us). However, generating good maps is a really difficult problem which really hasn't been available until more recently so I think that there are many improvements to be made here in the future.

I think we will see even more of this in the future. Perhaps a lot more free-roaming, sandbox games like Minecraft, Terraria or perhaps Project Zomboid 3 (video included since it's not that heard of and 'only' in beta). I think the procedural generation of content adds greatly to the sandbox survival genre of games. These games often add a bit of a RPG element to them, making it extra sad when your heroine/hero dies.

Taking it one step further, I'd love to see what happens when not only the maps are generated, but also the creatures within them. I imagine something like Spore 13 for monsters/creatures in the world. Perhaps someday one will be able to generate quests and dialogs aswell. It all comes down to breaking it into small enough parts I guess.

Hopefully we will se a lot more AR-/VR integration in games as well. Games played on devices such as Oculus Rift, Google Glass and so forth, are games I'm already greatly looking forward to, since procedural creation might be very applicable to such scenarios. For instance generating content based on whatever you are currently looking at.

Data-driven approach, Nov 15   game design

A data-driven approach is shifted from Object Oriented approaches. The data-driven approach seems like a really good fit if you are geared towards making a state-of-the art game engine for making really high performing games. Bitsquid is certainly outstanding in that sense

It's always a bit tricky when you're learning a new programming paradigm. Usually you learn a new programming language together with the paradigm which can help you understand difficult patterns and ideas more easily. However when shifting to the data driven paradigm, you haven't really got the advantage of changing language as well.

According to wikipedia 14, there are a few languages which have a more data driven approach but I have unfortunately not used any of these (except for one line of awk, but that's it). I'm guessing what we're after is to learn the concept and then embrace it in whatever language we are most confident. Techniques like loop unrolling and cache optimizations through padding are worth noting in the back of your head.

I'm still kind of eager not to do this first. Since I'm already pretty much into the object oriented paradigm, I'll probably prototype my idea with OOP on beforehand, then afterwards evolve it into something a bit more suitable to the profiling tools. I feel that the most important thing is that the game gets created in the first place and then one can make gradual improvements.

Software development model, Nov 12   game design

I think the model used to develop a game is really depending on what type of game you make. I'd like to address the fact that not every type of game needs to be high-end performing. As a guideline though, whatever type of development model which allows you to be productive is useful.

Do you have a ton of ideas which needs to be tested before you can decide upon stuff? Like /u/RukiTanuki suggested on Reddit to the girl making a science-based dragon MMO 15; There are several ideas to take into account.

The one i liked the most of his proposals is where he suggests that you make some prototypes/mini-games before you make an actual game. This allows you to evaluate concepts early and decide how they feel/what they add to the game in general.

I think another important thing is the interaction between the asset management and the development team is crucial. Using an internal wiki as a design document might be suitable for a small game making team. This might extend into a public wiki aswell which can help players in the game.

Me and some friends will probably start working on a game sometime soon, and we're currently discussing this a lot. I'll definitely recall and reuse the idea about getting a head start and something playable as soon as possible.

Haven and Hearth, Nov 8   game design

Today I played a game by originally made by Seatribe called Haven and Hearth 16. It's a MMORPG where death, Permanent death(!), is imminent. The scenario takes place in a world quite similar to real nature. There are no fictive elements in the game in that sense. It's really like a simulation of a subset of the real world. Typically you travel around in a forest of some sorts. There are mountains, rivers and lakes for you to explore. I starved to death pretty early but on my second character I managed to find some apple/hazel/mullberry trees which I could forage for edibles.

Other than permadeath, another unique thing about this game is that the world is dynamic. For instance can everything be razed and reused much like in the real world. I think this adds a bit of spice to the game, as MMORPGS tend to get very repetitive with new characters, as you do the same types of quests over and over again.

In order to make it more enjoyable and so on, Seatribe have added a quality system to the game. The quality systems gives value to the items much like an in-game currency. All of the items have quality values. If you combine items of different quality level, you get an item with some weighted average quality.

Their business model is quite interesting. The game is F2P 17 and doesn't focus on money making at all, which is quite a relief when playing. No ads, no worries. In a sense, it can get very "zen" as you stroll through the forest, enjoying the view. A meditation of sorts. This is really a good game for whenever you feel like escaping reality.

I've never played a game like this before. I've only played MMORPG's with a static world like Runescape 18 . Playing was really fun, I managed to find my friend there and we chopped down some trees together and built a simple shelter. Perhaps we should've played some more, since we didn't get that far in the game.

What type of gamer are you? Nov 5   game design

My name's Anton Erholt and I've just started my master's programme in Computer Science at KTH. I'm 23 years old and live in a suburb of Stockholm together with two of my friends.

I've been playing computer games for about as long as I can remember. I remember the Christmas when I got my first console, the Nintendo Game Boy 19 together with Super Mario Land 20.

Ever since then, I guess I've been kind of hooked on handheld games. Somehow, I really prefer the compact format and (the usually) somewhat simple controls. I can recall playing in the backseat of the car as a kid almost every vacation trip we ever made.

Throughout the years, I've owned a few different handheld consoles, mostly from the Nintendo series. IIRC, I currently own a Game Boy, a Game Boy Advanced (GBA), a PlayStation Pocket (PSP) and well, no PS VITA, but a PlayStation Certified smartphone 21. Together with my flatmate, we have some other consoles at home as well (NES, SNES, N64, PS3, XBOX [original] and a… Commodore 64!). As of right now I mainly play on my smartphone or my PC if I play something.

My favorite genre of games usually varies a bit, but over the years I seem to return to the single player RPG-genre. Games such as Golden Sun 22, The Legend of Zelda: Links Awakening 23 and Final Fantasy VII 24 are a few of my favorites. Another genre which I've grown a bit attached to, is the roguelike, dungeon-crawling genre. Permadeath, tons of monsters and weird actions. Dungeons of Dredmor 25 is one of the games I'm currently playing a lot.

One of my greatest game experiences must have been while playing Pokémon Blue 26, getting the 151st Pokémon. I remember being extremely happy about having "Caught them all". The feeling was almost indescribable after having spent so many hours completing that task. Too bad it only took 'til a few months until they released about a hundred more Pokémons in a new game.

One of the worst gaming experiences I've had was probably when I played one of the Zenonia 27 games on my phone. The game was so focused on trying to sell me stuff and incorporating ads that it was almost unplayable. I uninstalled it very quickly since it wasn't that fun. I'd rather had spent some money on buying the game instead of having a f2p business model.

I've not got that much experience of developing games. My main development work has been of web programming nature (part front-end, part back-end), so this is a bit of a new field for me.