The fastest growing genre in video games is "brain training," a genre no one had even heard of before last year. But it only takes one smash hit — in this case, Nintendo's "Brain Age" — to launch an armada of imitators.

Nintendo's rivals have tried to hop on the "Brain Age" bandwagon with copycats like "Brain Boost," "Brain Genius," "Brain Juice," "Brain Challenge" and (for the sake of variety) "Mind Quiz." The only person who might need so many brain exercise games would be someone who was dumb enough to buy them all.

The jury is still out on whether these games — consisting mostly of simple, rapid-fire math, logic and observation problems — really make you smarter. I have my doubts, and I'd be willing to bet that your brain gets more of a workout playing "The Legend of Zelda" or "Halo." I'll try to answer a more important question: Are brain training games any fun?

n "Big Brain Academy: Wii Degree" (Nintendo, for the Wii, $49.99): Nintendo's latest mental workout picks up where last year's DS hit "Big Brain Academy" left off. It presents a collection of 15 problems; the faster and more accurate you are, the bigger your "brain size."

The Wii introduces a couple of entertaining multiplayer modes, letting you challenge your friends to see who can solve the most problems in the same amount of time.

The biggest drawback to "Wii Degree" is the limited number of activities; a $50 product ought to have a lot more than 15 minigames.

Grade: HHZ\x (out of four)

n "Hot Brain" (Midway, for the PlayStation Portable, $29.99): Hot Brain may sound like a disease, but in this game it's the goal: Raise the temperature inside your skull by solving another batch of 15 problems. Again, that's not enough for a full-price game, although "Hot Brain" does add some language challenges, such as matching rhymes or putting words in alphabetical order.

Grade: HH (out of four)

n "The New York Times Crosswords" (Majesco, for the DS, $29.99): Millions of people get their regular brain workout from the old-fashioned, low-tech crossword puzzle. The premier puzzle in the United States appears every day in The New York Times; this package collects 1,000 crosswords from the Times archives in one slender digital package.

Logically enough, the puzzle clues appear on the DS' top screen, the crossword grid on the bottom. You can zoom in and out of different sections of the grid, then either type your answer with an on-screen keyboard or write it with the stylus

With hundreds of hours of fun, this is a great bargain.

Grade: * * * (out of four)