In the mid-70s, my then-girlfriend Catherine told me about a multi-player word game she used to play with her family that they simply called “the five-letter word game”. Actually, it’s more of a logic puzzle using words than a word game: each player choses a secret five-letter word and the others take turns guessing the words. After making a guess, the other players would respond with a number indicating the number of letters that my guess had in common with their secret word AND which were in the same position. This is NOT Hangman! It’s a lot more challenging than that because you’re not told which letters you guessed correctly; you have to apply logic to figure that out.

I started playing it with her and her brother Patrick and I was hooked. I couldn’t couldn’t get enough of it. I played it with Catherine and Patrick whenever they were willing, but secretly wished I could play against a machine, since humans occasionally make mistakes by responding to a guess with an incorrect count and also because I didn’t want to have to pester someone to play!

Fast forward to 2013, when I wrote the original app, which I called “Five-to-Go”, for Android devices. I wanted the game to be as challenging as possible, so I thought long and hard about the best way to play the game and implemented a strong playing strategy for the app. Over the next seven years, I refined the algorithm to the point where the app is playing a nearly-optimal game; in order to beat the app, you have to play almost perfectly or be lucky with your guesses!

I also implemented a rating system, modeled on the Elo chess rating, whereby points are won or lost at the outcome of a match depending on the respective ratings of the two players involved. For example, a player at the Novice level would get 50 points when beating an Expert, but give up only 2 rating points on a loss.

After Five-to-Go had been out for awhile, fans told me they wanted to play other people, not just the app, so I implemented a two-person player mode using home-grown server code that I wrote and which ran on Amazon Web Services. The server code managed communication between the players, but, unfortunately, was unreliable and I was never able to get it to work consistently; plus, maintaining the server on AWS was extremely expensive. Therefore, I shut down the app in 2018, vowing to rewrite it using the Google Firebase platform, which promised much lower operating costs, better reliability and richer functionality. My girlfriend, Dominique, suggested a better name: “Pento”. The advantages of “Pento” over “Five-to-Go” were brevity, a cross-cultural and cross-linguistic appeal, rather than uniquely English; as a bonus, “Pento” was even a five-letter word! I later chose to change the name slightly to “P3nto”, in order to make it easier to find in Google Play and the Apple App store (an iOS version is in the works and should be out shortly), and also to highlight the number aspect of the game.

The Android version is available for public testing and so far, there are no outstanding bugs. If you’d like to help us test P3nto, drop me a note at ruomini@gmail.com or message me. You will need a phone or tablet running Android version 4.4.2 or later and a Gmail account (this last is a Google requirement for testers).