There is a free game sweeping the world, and it’s making a lot of money.  “Puzzle and Dragons” came out in Japan in Feb. 2012 and was released in English and Korean shortly after. Recently it celebrated its 20 millionth download.

The game is a major moneymaker, averaging $3.75 million in revenue per day, as of last April. The company that publishes the game, GungHo Entertainment, has more money on hand ($15.1 billion) than Nintendo, EA, or Zynga.

With more than 13 million downloads, in Japan alone, the numbers seem to indicate that more than 10 percent of the country’s population plays the game. Not satisfied with being the top-grossing game on iOS and Android, GungHo Entertainment is looking to branch out to the Nintendo DS as well.

According to some sources, the success of this game has a sinister edge. Like many free games, “Puzzle and Dragons” has an in-game currency that you can earn slowly by playing or instantly by paying.

At first, the game is skill-based, but your skills can only take you so far. The artful transition from skill play to pay-to-play sucks many players into spending hundreds or thousands of dollars on this, seemingly, elementary game.

Regardless of what you think of the publisher’s tactics and motivations, Puzzle and Dragons is as unquestionably successful as it is entertaining.  Some may even go so far as to call it addictive.

Why not download it and give it a try … first play is always free.