Tech in Laser-Tag LARP

From the beginnings when it adapted an 80’s toy, Laser-Tag LARP has always used technology as a fundamental part of the overall game experience. Other technology has been used as part of games from PSION II’s to today’s microcontroller controlled devices. “The Goodman Protocol” was a LARP that ran recently and features both RFID and GPS technology as part of its props.

Translating an Alien Language

The game centred around a potentially alien tablet with a language that needed to be translated. Traditionally this might have been done using some kind of cypher with a suitably alien looking font. The main alien tablet was constructed from two polystyrene sheets, the top one was suitably carved with an ‘alien’ language (we did use a font to help with the design but it doesn’t mean anything). RFID cards were then ‘sandwiched’ between the two layers. The prop was then painted to give it a ‘stone’ effect and then it was cut into segments as the game called for it to have been ‘broken’.

The completed tablet

The other half of this process was the actual translator device. This was powered by an Arduino Nano with a 4×16 LCD screen for output and an MFRC522 RFID reader in a separate housing. There was no reprogramming of the actual cards needed as my first intention had been purely to read the UID (Unique IDentifier) of the card and then display corresponding text. The first version of the software would read the card and then just display the text. I have to give all credit to Dave Barnett who (after I asked for help) offered to take a look and not only implemented single line scrolling text (which I had been struggling with) but then also added a learning system.

The Languatron booting up

How this worked is as follows: –

  • A Tablet Piece is scanned (you place the reader over the tablet piece and then press the red ‘analysis’ button on the top of the device).
  • If it has not already been scanned then it adds to the overall “Rosetta-Z” score, this score is then written to the EEPROM part of the Arduino. This score is then loaded when the device is turned on so its persistent between power offs. To blank the score (ahead of actual game use) you would turn the unit with the analyse button pressed in until the display says “Rosetta reset”.
  • Compare current Rosetta score and then display relevant text where the score matches.
Scanning a tablet piece, you could potentially read it from the top but this produced inconstant results (even with a modified reader)

So each card (or tablet piece) has a line of text associated with the UID of the card and depending on what the current Rosetta score is depends upon which line is shown. For example, the first tablet piece would show the following text depending on what the current score is, the last entry is the correct translation. Each piece (the first time it is translated) adds 2 to the overall Rosetta Score (which is displayed as a % on the device): –

  • 5, “When the Sun is right”
  • 8, “Just after the position”
  • 16, “When you are ready”

As the minimum score for any piece is 5, this means the first two times the device scans any item it would return the error “Insufficient Data” as the Rosetta needed to be a minimum value to return any data. What this also means that all of the tablet pieces would be needed in order to get the correct final message (at least two were not immediately available when in play).

Analysis result, the T-Score indicates a high degree of certainty that the translation is correct.

The amount of time the device took to do an analysis was fixed at two minutes so it would around 20 minutes to do a scan of everything. This was initially 6 minutes but that felt like an eternity in initial testing. Looking back we could have had a fixed time + variable based on Rosetta score, so the early analysis would take longer and when you had more pieces the analysis time would be faster.

GeoLock Box

The ‘box’ booting up

This was a build inspired by a project as published on Alistair Aitchison’s excellent YouTube channel, PlayfulTech. The actual video where he demonstrates his is here: Take me Home box.

On the outside this is just a cheap wooden project box from Amazon with a key switch and two line lcd display. Inside the box is a battery, Arduino Nano, GPS Module, Relay and Maglock. I used pretty much the same parts that Alistair uses on his and he has a parts list on the above linked youtube video.

The inside of the box.

What this actually does is that you put whatever game related item in the box, close it so it locks and leave it to be discovered. When the players find it (I had a separate puzzle locking away the key for the key switch), turn it on, wait for it to get a signal fix and then they have to take it to the location that’s been encoded onto it for the box to open.

Acquiring a signal

As there’s no compass, only a distance gauge, you initially have to walk around figuring out which direction to go in. When you get to your destination the box unlocks automatically. The destination can be changed in the Arduino code (the video goes into how to use Google Earth to get your coordinates). There is a variable in the code so the box opens when within a certain distance of the final destination (I had mine set to 10 metres.

The display with a GPS fix showing current co-ordinates and distance to target, this is still configured to the actual site where it opened in the game.

The only issue we had was that when the players got it powered on they thought it might not be working as it seemed to not be getting a fix. It can be slow to get a fix but after a few minutes it seemed fairly reliable.

The backup hole where you can get to the emergency release lever if you leave site with the box still locked.

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