• by Gavin O'Malley  @mp_gavin, March 24, 2009

Shockwave.com, a unit of the Nickelodeon Kids and Family Games Group, on Tuesday launched a subscription-based online gaming service for adults.

Casual games like solitaire and Tetris, which are catchy and have a short learning curve, have experienced a huge surge in popularity in recent years.

"There has been explosive growth in online casual gaming in the past couple of years," said Dave Williams, SVP and general manager at Nickelodeon Kids and Family Games Group. "ComScore says that today, 86 million Americans visit online gaming sites compared to 67 million in December 2007."

Demand is so great, in fact, that Shockwave is betting users will pay money in return for more control and rewards. "People want to connect and be rewarded for the time they spend playing games," Williams added.

For $29.95 per year, Club Shockwave offers subscribers hundreds of "skill games" and puzzles, along with opportunities to win cash prizes and to accumulate rewards for time spent online. The service initially launches with 12 skill games and hundreds of puzzles. The site also offers community features.

The launch of Club Shockwave coincides with the relaunch of Shockwave.com, which serves some14 million monthly visitors, according to Omniture SiteCatalyst data. The new site features ratings and reviews, along with personal profiles.

Casual games are attracting roughly 200 million active players per year, and take in about $2.25 billion, according to a recent Casual Gaming Association report. The CGA also found that the market is growing at a rate of about 20% per year.