Taking inspiration from American Spelling Bees, Spellathon launched online a month ago as the world's first digital spelling championship. It has since been played in 90 countries with over 800,000 words spelt correctly.
The service has now expanded as a free app on iPhone, iPod Touch, iPad and Android devices, available exclusively for one week on the GetJar independent app store service.
Set in a futuristic digital universe, Spellathon is presented by 'The Professor', a 3D bee character voiced by Stephen Fry. Players of all ages can compete against the clock and others to spell a number of words correctly. All successful spellings are then "banked" in your hive and high scores are ranked on the global leaderboards.
Android and iOS players can also qualify to compete against Fry online at the global championships in March 2012.
The apps and online site raises money for Mencap via the JustGiving fundraising service. Users earn a new 'Spelling Bee' every time they raise £3 for Mencap, including DJ Bee, Fashion Bee, Princess Bee, Pirate Bee and Angry Bee.
Fry said: "This is just about the best integration of imagination, education, technology inclusiveness and fun that I've ever encountered. Very proud to have been involved in it, even in the smallest way."
Mencap assistant director of fundraising Hazel McIlwraith added: "Spellathon has been a successful, paper-based event for the last 18 years.
"Now, by applying online via laptops, mobiles, tablets and whiteboard technologies with state-of-the-art 3D animation, we have the opportunity to take it to a global audience.
"We are delighted to bring Spellathon to new audiences and to increase support for people with a learning disability. All funds raised will make a real difference to the lives of people with a learning disability."
Fry will host the first-ever global Spellathon Championships, taking place virtually from March 5-11 2012. Entrants will have 15 minutes to record the longest word run of correctly spelt words. Digital trophies and prizes will be awarded to the winners and the players who have raised the most money for Mencap.