Rather than showing a number of letters for a word to guess, Worldle (note the extra L) shows you a black shape representing a country somewhere across the globe.
Based on the shape and size, gamers must guess the country based on their knowledge of the world map.
If your guess is wrong, the game gives you a percentage representing how close you are to the right answer, plus the distance in kilometres that the real country is from the one you guessed - meaning you can get closer and closer within five guesses before your sixth and final try.
Geography and travel fans have been puzzling over the game since 27 January, when its French web developer creator, Antoine Teuf, launched it as a bit of fun.
He gives a nod to the original format on the website, saying: “WORLDLE has been heavily inspired by Wordle, created by Josh Wardle.”
“A few weeks ago, I discovered the original Wordle and I instantly loved it,” Teuf told The Independent.
“I really appreciated how effective and simple it was, and love how it allows everybody to play together with a simple sharing of the result as a small text with emojis.
“That's why I decided to do a geographical variant. After talking with my girlfriend about it, she reminded me of this old Facebook game called GeoChallenge where you had to guess a country by its shape.
“I made the game in just a few days.”
He was astonished when, after a few weeks, its daily players reached 1,000. Now those numbers are in the hundreds of thousands.
“Yesterday 970,000 people played Worldle! It's insane!” wrote Teuf on Twitter in February.
It’s not the only geography quiz to take a leaf out of Wordle’s book - another daily map guessing game, Globle, launched on 30 January with a slightly more complex format.
This time, you guess a country to start the game, and your chosen country appears in a colour ranging from pale pink to red to show how close it is to the country of the day.
Without the distances that Worldle gives, it’s much harder to get the right country in just a handful of guesses, but the game is much more visual.
Creator Abraham Train came up with Globle in mid-January as a project to test out his design and programming skills.
“It’s inspired by Worldle, of course, and the geography games on Sporcle,” says Train, who is currently looking for web development work.
“I’ve heard nice things from all sorts of people, including travel fans, but the kindest feedback comes from geography teachers who want their students to play. I’m delighted to see the game being used in education; it means the world to me - pun intended.”
Social media users are sharing their delight and confusion at both games daily.
“After 13 guesses I had to consult a map and it STILL took two more guesses!” marvelled Globle user Brent Black on Twitter.
“Our Wordle family group chat has turned into a Wordle Quordle Nerdle Globle Worldle group chat,” joked Dr Katie O’Connor of the many Wordle spin-offs.
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