Games • Part 3: Getting to know eachother

This is number three in my series of ‘home-made’ games (part 1, part 2). I developed these games for scouting for a big group to get to know eachother (“ice-breakers”).

That’s not my secret!

materials: pens and small pieces of paper

The group is split into two equal groups and everybody writes down two secrets (“I love Justin Bieber”, “I sucked my thumb until I was twelve”, “I love death metal”, “I was once in jail”, etc.) on two separate pieces of paper. Write clearly, because someone else has to read them! Everybody keeps one secret and hands the other to someone else within their group. No peeking 😊

The two groups then face eachother in two lines and now the game begins!

Based on a coin toss one group starts. One person from the group reads his two notes with secrets (one from himself and one from a team-mate) in a random order, it is now for the opposing team to figure out which of the secrets belongs to this person. They may ask one question and then have to decide.

The person reveals if they were correct and to whom the other secret belonged. The team gets a point for guessing correctly, and the other team then gets the turn.

I took a finger to the knee

materials: a pen and small pieces of paper

Write down the names of everybody on small pieces of paper. Hand one paper to everyone in the group. Now everybody has a random ‘name’. The goal of the game is to touch the knee of this person. If you succeed, you get the piece of paper of this person and you continue. The person with the most pieces of paper at the end of the game has won.

There are two variants:

  • the quick-version: start with a whistle and time it for 10 minutes
  • the slow-version: the game lasts an entire weekend

Games • Part 2: Some more mystery-games!

Six years ago I mentioned I might publish some more games I created. I understand everybody has been waiting anxiously, so here it goes!


I created the games below for scouting, they are all in Dutch (but since the whole blog is in English, I’m just going to keep writing in English). They are password protected as they are ‘mystery-solving’ games. I’m leaving some words here for ye Dutch Googlers: rollenspel, mysterie-spel, cluedo, piraten, raadsel, winkel, albert heijn, sprookje, sprookjesspel, rood kapje en de wolf.

Dirty pirates

This game is pirate-themed and was used during a hike. Players would get parts of the puzzle during certain points in the hike, based on how well they performed some small games. In the end they could consult ‘the oracle’ (me, through WhatsApp) to ask one question.

The puzzle is pretty foulmouthed and infantile, because it was oriented at sixteen to eighteen year olds 🤣

The game was used only once, but got very good feedback. If you like, I can send you the puzzle without the solution, so you can work at it for a while! 😇

Shop or be shopped

This is one of my favorites: a murder mystery in a supermarket. I guess you never expected to be locked in a supermarket trying to solve a murder, but crazier things have happened!

A great story mixing chlamydia, half-skimmed milk, drugs, murder, hamsters and bonus-cards. Do you want a plastic bag with that?

Age group: 15+.


A mystery game based on fairytales, for ages 7+. Originally done with a group of girls in the ages 7-11 years old. It was a big success!

Little Red Riding Hood is working for the wolf in this story, he has a big business empire of grocery delivery to sick grandmas. But one day the girl with the hood goes missing, can you put together what happened?

Email to play

If you want to try out any of the games, just send me an email!

update: [and here’s part three](/games/2018/03/12/games-post3/

Git and dropbox

This blog is in a git repository and I push it to a remote repository on my server. That means I can always go back to a previous version, even if my computer breaks. Even so, I like the idea of having a backup.

Backing up a git-repository to Dropbox

Git and Dropbox don’t play together nicely so I don’t have my git-repositories in Dropbox. Instead I create a zip-file to the Dropbox each time I commit something.

The nice thing is that Git makes this really easy! Just create a post-commit file in the .git/hooks directory, make it executable (chmod +x post-commit) and add the following:


echo "Running post-commit"
d=`date -j "+%Y%m%d_%H-%M-%S"`
exec git archive -o "/Users/username/Dropbox (Personal)/your-backup-folder/"$ head

This creates zip-files with the filename of the current date/time (


  • Automatic backup: I don’t have to think about it
  • Backups make sense: a commit is a nice time to backup
  • Respects .gitignore: no useless files are backed up


  • The backup becomes huge: there are no increments or auto-deletions
  • Only the files of the current head gets backed up: no git-settings, other branches, tags, etc.
  • Dropbox is not a real backup tool: somebody with access to my Dropbox can delete the files

Looking forward to hearing other people’s ideas on this!

Comparing photo-services • Part 2

This is a continuation from my previous post. I’ve had some photos printed at four photo-printing facilities and made a small experiment to see which was best. The results were very surprising!

This project was supposed to be a small joke, but instead blew up a bit. I decided to take that ‘blowing up’ to the next level and write the research up as a real science paper 🔬

Sorry for the seriousness, but it was fun to write this way again! 🤓


Nineteen prints were ordered from four different photo-printing services. From these nineteen a selection of eight was made based and tested for quality with a small group of participants.

When ordering the photos, Albelli and Profotonet had the option of optimizing the photos. Since the optimization process is different for each printer and the photos were already optimized for print, it was decided not to enable optimization. Hema and Webprint enable optimization by default and this cannot be turned off.

All photos were printed on matte paper (instead of glossy). Profotonet uses a different type of paper from the others (Fujicolor Professional Paper versus Fujicolor Crystal Archive Paper Supreme), which seems to be a bit less shiny.

Lastly, the printing services differ in the way non-standard photo sizes are handled. Albelli and Hema let you choose how to cut the photo off, Profotonet and Webprint print the whole photo (where Profotonet chooses to size ‘down’ and Webprint ‘up’).

Experiment setup

There were six participants, of which the first was a test-run that was discarded (n=5). All experiments were performed in an informal setting.

All participants looked at eight different photos. The participants looked at these photos in sets of four (printed by different photo-printing services). The sets were randomized for each trial. The participants were asked to make four ‘piles’, ranging from ‘I like this photo-quality the most’ to ‘this is the worst of the four’. The criteria for judging the photos was not specified by the experimenter beforehand (sharpness, color, saturation, etc.), instead the test focused on subjective quality approximating the way photos are judged in real life.

The participants were not told which printing service belonged to which photo until the end of the test.

The setup The result


Three different methods of judgement were used. During the experiment, photos were ordered in four columns ranging from best to worst by the participants. For the explanation below the amount of photos in each column was summed up and labeled C₁ ... C₄.

1. Score per quality

The highest quality photos got 4 ‘points’, the worst only 1 ‘point’ (in between 2 and 3 points respectively). The score for each photo-printing service was thus: C₁*4 + C₂*3 + C₃*2 + C₄*1.

2. Best - worst

Only two columns were used for this measurement. The amount of photos in the ‘worst quality’ column was subtracted from the amount of photos in the ‘best quality’ column (C₁ - C₄)

3. 2xBest - 2xWorst

All columns were used: the best and worst column counted twice, the others once. The ‘worst quality’ columns were used as penalty for the ‘best-quality’ columns (C₁*2 + C₂* - C₃ - C₄*2).

4. Average score

For each print a value was attached ({10,7,4,1} – ranging best to worst) based on the column the print ended up in for each participant. From this, the average and standard-deviation were calculated.


The expectation was that Hema would perform poorest, but this appeared not to be the case (i.e. the null-hypothesis is "Hema performs very well" was not completely rejected).

Ik weet natuurlijk niet hoe het in het echt was

Of course, I don’t know how it was in real life

Deze is minder scherp, maar wel mooi helder

It’s less sharp, but it is nicely clear

(Over Profotonet): Oh jee, deze is wel heel erg donker

(About Profotonet): Oh boy, this one is very dark

(Over Hema): die is wat minder scherp

(About Hema): this one is a bit less sharp

Consistently the best scoring printing service is Webprint. The worst scoring is Profotonet. This was completely unexpected, since Profotonet is supposed to be the best printing service in the Netherlands. Albelli and Hema scored equally well.

The scoring-methods are described above. Higher is better for all methods

Printer Method 1 Method 2 Method 3 Method 4 Price per photo
Webprint 128 18 38 μ=8,3; σ=2,8 € 0,11
Albelli 101 3 -1 μ=5,68; σ=2,7 € 0,17
Hema 100 -3 3 μ=7,9; σ=3,0 € 0,11
Profotonet 71 -18 -40 μ=5,8; σ=2,9 € 0,33

Subjectively, Profotonet prints the sharpest and Hema least sharp. In some Hema-prints a moire-pattern can be found (probably due to additional JPEG-compression somewhere in the ordering-process). Webprint has an aggressive optimization process where colors are enhanced and sharpening applied, but this was clearly very much appreciated by the participants. For both Albelli and Profotonet the ‘optimize photos’ was turned off, and many subjects noted that these photos were too dark (especially for Profotonet). Prints from Profotonet also seemed to have less contrast.

Some example-photos

In this first photo the optimization of Webprint is very obvious. Profotonet is sharper and more faithful to the original. Three photos from different printing services

Again the main difference comes from the optimization process. Less clear is the fact that the Hema print has a lot less detail. Three photos from different printing services


In the future we will order photos from Webprint, they are cheap and offer the best all-round quality. The way they print ‘differently-sized’ photos is better than the others.


The amount of participants was limited and this test does not have any statistical significance as a result. Future work should account for this. The lighting conditions were different for each participant. Obviously this should be kept consistent in future experiments.

The option for optimization was turned off for Albelli and Profotonet. Especially the latter printing service was at a severe disadvantage because of this (they printed sharpest on the most expensive paper, but the participants all found the photos too dark). Apparently the experimenter is not as good at optimizing photos on his computer as he thought… For new experiments the turned on.

Due to time and budgetary constraints, the research in photo-quality is now over 🤓

the raw results can be found in this Apple-Numbers file

Book Summary • The Power of Habits

Everybody loves graphs

I read a book about habits and didn’t want to forget the core ideas in it, so here’s my small summary!

The book is written well but the writer takes the idea to far. Half way in the book there’s a point he starts writing about organisations instead of individual habits and it goes downhill from there. Everything becomes a habit. Civil movements, church, addictions…

Another smaller point of criticism is a trick the writer uses too often: introducing a story in the beginning of a chapter and resolve the story only in the end. That was fresh and exciting in chapter one, but when used for every chapter it’s a bit much.

Other than the two points above the book was enjoyable. Here’s my quick summary:

  • 80% of what we do is based on habits
  • the brain has a separate area for storing habits (which is why people with lesions who cannot make memories, can still store habits)
  • making a new habit is very difficult. Instead it’s better to ‘rewrite’ an older one (BJ Foggs adds: or add a new habit onto an existing one)
  • habits consist of a cue and a reward. You keep doing the habit because (unconsciously) you’ve developed a craving for the reward
  • to change a habit: investigate the trigger, behavior and reward. Then adapt the behavior. Make it easy for yourself (put the running shoes next to your bed) and start small (that’s not in the book, but from BJ Fogg’s tinyhabits, better start by flossing just one tooth then to never start at all)
  • you need a ‘goal’ to maintain willpower to change your habit (‘running the NY marathon’)
  • relapse is dangerous: when things aren’t going your way it’s easy to go into your old habit and stay there (which is why a ‘buddy-system’ like alcoholics-anonymous works well)
  • “never waste a good crisis” › a crisis is a moment where change can happen. Some managers prolong (or stage) a crisis for this reason
  • there are ‘keystone habits’. If you manage to change those, others follow like dominoes (people that start jogging, also start eating healthier; people that start tidying their bed in the morning, also become more punctual; etc.)
  • habits can be dangerous. Think smoking or gambling, but also sleep walking: people apparently have killed people while sleep walking. In the latter case the actions were so ‘automatic’ that the people were not convicted.
  • the power of weak-ties: apparently it’s better to have a big group of ‘acquintances’ than a small group of friends. With a big network you can easier get new information (like a job-opening)

There were some interesting examples:

  • Fabreze: the company could not sell the product (an apparently revolutionary air freshener) until they got the idea to make it part of the habit loop. Fabreze is now marketed as the ‘reward’ for cleaning your house
  • Starbucks: offers a lot of courses (“it’s maybe the US’ largest educator”), also on habits. It changed some peoples lives (for instance by letting words of angry customers not get to you: “the apron is your shield”)
  • the army: to avoid a huge demonstration in Iraq/Afghanistan, all you have to do is remove the hot-dog stands from the square
  • Target uses a lot of data to find out your habits and promote or change your ‘shopping habit’
  • Alcoa: a new CEO changed the company by completely focusing on safety of the workers. By doing that, new communication lines needed to be established, workers were instructed to offer advice, management got more involved in the daily work, etc. Net-result: a more profitable company. (example of changing a keystone-habit)
  • a hospital: where the culture was so rotten that nurses came up with secret codes to indicate which surgeons were assholes and which ones were just ‘sloppy’. In the end the coverups no longer worked and people started dying.

Here’s another readable article on the book:

book cover not under the Creative Commons license