Electronic Arts is facing strong criticism over the in-app payment system in its Dungeon Keeper game.

Many said the game was "unplayable" unless they spent significant sums to speed up progress and get upgrades.

EA said it had designed the game to fit in with typical patterns of mobile play and people did not have to spend money if they did not want to.

Peter Molyneux, maker of the original Dungeon Keeper, said EA had not got the game's balance right.

EA released the mobile version of Dungeon Keeper early in February and soon afterwards it started to get negative reviews on many tech news sites.

Reviewers criticised the game's aggressive use of in-app purchases which involve paying real money for an in-game resource called gems.

Reviewer Jim Sterling from The Escapist said the constant need for hundreds of gems undermined the game's claim to be "free to play".

"It's free to wait, but not to play anything," he wrote. "There's nothing to actually play."

BBC News