If you’re bored of crosswords and sick of Sudoku, an enigmatic new riddle game may be just the mental challenge you need. A mysterious app called None* gives users only one clue to get started and a keyboard to type their guesses. There are no images, music, animations, sound effects or hints to help users, or indication of what the purpose of the game is exactly. Scroll down for video . An intentionally mysterious app called None* gives users only one clue to get started and a keyboard to type their guesses. Examples of 'questions' are pictured above left and right . Available for iOS, Android and Windows Phone devices, the description of the game in stores reads: ‘No one really knows what none* game is about.’ The free app has a pitch black screen and a single clue written in white text, as well as showing a small keyboard. Upon starting the game, there is no indication what the goal of it is, how many levels there are, or even how users are supposed to solve some of the more obscure riddles. However, the app can be completed and has 50 levels, according to people bragging on the App Store that they have completed the None* app. The questions are relatively simple to start with, including basic maths questions and others that have clear answers, but then extend to name associations, before seemingly showing random statements and even coordinates. Available for iOS, Android and Windows Phone devices, the description of the game in stores reads: ‘No one really knows what none* game is about.’ It is intentionally more mysterious than a crossword (stock image) and does not have as descriptive clues or aids of hints or images to help players guess the answers . The app is available to download for iOS, Android and Windows Phone devices. Players are confronted with a black screen and a single clue written in white. They use the keyboard to enter their answer in order to progress to the next level. There are 50 levels in total in 'Episode One' and clues get progressively tougher. But upon playing the app, this is not known and  it seems mysterious. The app's inventor, Dimitris Chassapakis, said that around 10 per cent of people who downloaded the app have completed the puzzle game. Clues include: 'The ultimate question of life, the universe and everything,' 'P + left step 1 + left step 7 + right step 1 + right step 1' and 'the answer is next. The next is answer'. Then there is a blank space beneath the clue to write the answer. Athens-based Dimitris Chassapakis, who created None*, told Business Insider that it’s his first text-based puzzle game for mobile. He said that there are 50 levels in None* but just 10 per cent of players have completed the game. ‘This is the first episode and if you solve all 50 levels you can subscribe for the release of Episode 2 — probably this summer,’ he added. Between 10,000 and 50,000 people have downloaded the free app via Google Play but there are no stats from the App Store. Reviews of the game on Google Play include those from people waiting for part two. The app has a pitch black screen and a single clue written in white text, as well as showing a small keyboard. The questions are relatively simple to start with, including maths questions and some that have clear answers, but then extend to name associations, before listing statements (left) and coodinates (right) A user called Aaron Hutchinson wrote: ‘While the game is a bit short, Episode 1 was a ton of fun. ‘Some of the clues had me thinking for days. ‘Once I stopped over thinking the clues, this became much more enjoyable. Can't wait for Episode 2.’ However, it wasn’t such a hit with others. Exasperated player Scott Rudell wrote: ‘Frustratingly vague "puzzle" game. None* refers to itself as a puzzle game, but that's a poor descriptor. ‘Puzzles have clues which lead to a correct answer. None* simply gives a single, usually insufficient clue without context, and you have to guess at which of the many possible answers is the one the game is looking for.’ Around 10 per cent of None* players have completed the app's 50 levels and are eagerly anticipating their second episode, but others were simply frustrated with it (stock image)
Enigmatic app is the brainchild of a developer in Athens, Greece .
It has a black screen with fiendish clues and no hints or images at all .
About 10% of players so far have completed the app's 50 levels .
Equally mysterious episode two of None* is expected this summer .