HUDSON — If concentration, deep thinking, quick calculations and serious strategizing were noisy affairs, surely the librarians at the Hudson Regional Library would be doing a lot of shushing on Thursday mornings.

That’s when the library plays host to Mahjong Morning, and players say few games require so much brain power. This is something evident from the facial contortions, squinting and lip biting going on at a recent session.

The players, mostly older, may actually be keeping their minds vital by playing, said Lori Lippman, who started the Mahjong group at the library in October.

“It’s fun but requires a lot of mental work,” said Lippman, who began playing the tile-based game believed to have evolved in China during the Qing Dynasty, which ruled from 1644 until 1912. “It keeps you really sharp.”

The play is held each Thursday, from 10 a.m. until noon. It’s played by three or four players, and several tables are set up at the library to accommodate as many as two dozen players — more during the winter months. As many players have headed back north for summer, but more than a dozen were on hand to play.

Lippman has been surprised by the interest.

“Who knew? It’s unbelievable how many come,” she said. “It’s the middle of May and we got four new players.”

Players in the group range from experienced to clueless when it comes to the game, which Lippman said can be a little daunting to learn. Fortunately, the experienced players and Lippman are on hand to teach.

The game uses tiles, some numbered, others with dragons, flowers and even the four winds. Players strive to create “hands” much like in card games, with hand-building accomplished through discarding tiles and picking up needed tiles from among the discards.

An interesting aspect of the game is that under the National Mah Jongg League, a New York-based sanctioning body, the game changes every April 1, and that’s no joke. It doesn’t change much, said Cecelia Szymanski, who’s been playing with the group since it started.

The National Mah Jongg League uses the two-word, two-g spelling of the game’s name, while the group uses the one-word, one-g spelling. According to the National Mah Jongg League, the annual changes apply to American Mah Jongg, which has several difference from Chinese Mah Jongg.

But they change just enough to ensure players don’t memorize all the winning combinations. They do this by throwing in some new combinations, or winning hands. Each player has a fold-out card that shows the various winning combinations, which they reference frequently during play to ensure they are angling for the hands that gives them the best change based on the tiles they have in their collection.

“I love it,” said Karol Spear, a regular with the group. “It takes thinking.”

Despite the concentration, members of the group keep it congenial and there’s always good conversation throughout.

“Nobody’s out for blood,” said Szymanski.

Fran Kranick had an idea of how the game is played when she joined the group but, having been away from it for a long time, was a bit rusty.

“I had the concept, but you forget,” she said. “I’m back into it now, though.”

Lippman said the group always welcomes new players of all skill levels, including no skills at all. Game sets are provided. The Hudson Regional Library is at 8012 Library Road, between Fivay Road and Hudson Avenue.

“You just have to show up,” she said.