Creating an Alexa Game: The Spark of Inspiration for Number Spies

A game about spies, coded messages, and numbers stations.

Encoding and decoding a message with a One-time Pad


When creating a game, there are many things to consider. How many players? Is the game genre adventure, RPG, puzzle game, or one of many other choices? What is the theme? Those are just some of the important questions that need to get answered, but for Number Spies it all started with the idea of re-creating the experience of a numbers station on a smart speaker.

Numbers Station

A numbers station is a radio station that broadcasts on shortwave radio frequencies and is used by intelligence officers to transmit encoded messages. Numbers stations have been used since World War I and throughout the Cold War and still exist today. Anyone with a shortwave radio can tune in to the proper frequency and hear the list of numbers that are being spoken, but only those with the proper tools can decode the message. One of the first transmissions that I heard was from the station called The Lincolnshire Poacher. It was fascinating.

Numbers Station as a Flash Briefing

After listening to a few example transmissions, I thought that it would be fun to create an Alexa Flash Briefing that simulated a numbers station transmission. It was a unique experience that nobody had yet done. The problem was, I didn’t know anything about manipulating audio. The idea was put on the back burner for over a year.

With More Research, the Idea Grows

During the months after the initial spark of inspiration, I spent more time researching not only numbers stations but also message encoding and decoding. The Flash Briefing could get away with generating random numbers that didn’t really mean anything because there would be no way that the message could be decoded. But what if you could?

As a boy, I had a notebook filled with different ways to encode messages. Behind a poster in my room was a map of the neighborhood with the best hiding places clearly marked. The more I thought of the possibilities, the more my boyhood games at being a spy came to mind.

What if the numbers station transmissions contained real messages that could be decoded?

What if the Flash Briefing was a piece of a larger spy game?

Encoding Messages

My research expanded to include code books, checkerboards, and one-time pads (OTP). I learned which part of a message transmission was encoded and which was not.

A checkboard is a way to convert letters, numbers, and punctuation into a number representation. A code book allows for numbers to represent words that are frequently used in messages. Neither of these spy tools need to be kept secret.

The key to secrecy is the OTP. Think of it as a notebook where each sheet is a list of random numbers. Only two copies of the pad exists: one for the sender and one for the receiver. After a message is encoded, the sender destroys the page. The encoded message can be sent as a numbers station transmission or left at a drop location. The receiver then uses the same sheet from their OTP to decode the message and then destroys the sheet. Each sheet is used only once. The messages are unbreakable without the pad.

A Bigger Spy Experience

Over the months, the idea grew from a Flash Briefing that pretends to transmit messages to a complete spy experience where real messages are encoded by OTPs and transmitted via a “numbers station” in both a Flash Briefing and an Alexa Skill and that players could take on the role of a spy that decodes those messages.

The player looking for the complete experience could manually decode a message using the OTP. The new player (or those looking for less time commitment) could use a web-based decode tool.

I started thinking of this experience as a spy themed puzzle game. Decoding messages would be one type of puzzle.

Decoding the message needed to be done outside the voice game, but there needed to be a way to report back that the puzzle was solved. Each encoded message would include a unique verify code. That verify code would be used in the Alexa skill to let the game know to give you points for decoding the message.

To learn more about decoding messages, watch Number Spies — Decoding Messages.


Number Spies started from the idea of a numbers station encoded transmission to a more complete spy experience where players can decode real messages and interact with an Alexa skill. It became clear that the experience needed more tools such as website and social media account. The result has become a form of Alternate Reality Game (ARG).

What has inspired you in the creation of your own voice games?

What spark of an idea do you have that is just waiting to be made into a game?


Creating an Alexa Game — Table of Contents

  • Intro — From Idea to Code and Beyond
  • The Spark of Inspiration for Number Spies (this post)
  • Number Spies — System Components Overview
  • Content Management with
  • Number Spies Alexa Flash Briefing
  • Number Spies Alexa Skill — Language Model
  • Number Spies Alexa Skill — Why I Chose the Jovo Framework
  • Number Spies Alexa Skill — Text-to-Speech and Speech Markdown
  • Website Domain Name and Skill Invocation Name
  • Number Spies Alexa Skill — Code (multiple parts)
  • Number Spies Alexa Skill — Unit Testing with Bespoken
  • Number Spies Alexa Skill — Skill Store Info
  • Number Spies Alexa Skill — Analytics with Dashbot
  • Number Spies Alexa Skill — Exception Monitoring with Sentry
  • Number Spies Alexa Skill — User Acquisition with Voxalyze Then Not
  • Number Spies Website
  • Game Promotion & Social Media
  • Is the Game a Success?



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Mark Tucker

Alexa Champion 🏆, Bixby Premier Developer, Software Architect, Speaker 🎙️, Author