(AP) -- Nintendo's add-on button device for its 3DS video game machine is facing criticism as a possible design flaw and a detraction for the already struggling portable.
Some critics say Nintendo Co. is embarrassed about the 1,500 yen ($20) "slide pad," noting President Satoru Iwata didn't mention a word about the gadget at his presentation earlier this week.
The device, which goes on sale in Japan on Dec. 10, works as another controller. It's handy to have for more complex games from outside software makers like the "Monster Hunter" series from Capcom Co., set to go on sale in Japan on the same day.
Five other games, including "Metal Gear Solid Snake Eater 3D" from Konami Corp., also can use the extra device. More games may be added to the list.
Nintendo, the Japanese manufacturer of the Wii home console and Super Mario and Pokemon games, says the peripheral part isn't necessary, just a matter of preference.
Adding it helps deliver a gaming experience more similar to a home console in remote-controlling.
Hiroshi Kamide, analyst at JPMorgan Securities Japan Co., believes Nintendo is displaying a surprising lack of confidence.
"It's a bit of a shame. Only six months after releasing a new platform they're having to come out with an attachment to make it more attractive for some people," he said.
Game fans were disappointed.
The part, although not massive, makes 3DS bulky and harder to carry around in your pocket, important for a portable.
No wonder the device was quietly introduced on the company website this week.
Iwata said nothing about the device during his presentation, although he delivered praise about the upcoming "Monster Hunter" and other games to a packed crowd at a Tokyo event.
The device has also been witnessed, but not displayed prominently, at the Capcom booth at the Tokyo Game Show exhibition, which previewed to media Thursday and opens to the public this weekend.
"I think it feels like too little too late, and it also confuses consumers," Jean Snow, a gaming expert, who writes about Japanese pop culture. "I do believe it was a design flaw not to include it."
Snow said having the additional controller makes a big difference in shooting games, and he expects the feature to be later included in a 3DS upgrade.
Competition in portable gaming is heating up with the arrival of Japanese rival Sony Corp.'s latest portable offering, PlayStation Vita, which already comes with buttons that work in a similar way as the 3DS new device.
PlayStation Vita goes on sale in Japan on Dec. 17, and early next year in the U.S. and Europe.
Both 3DS and PlayStation Vita face a threat from smartphones and tablet devices that also offer on-the-go games and other entertainment.
Nintendo has already slashed the price of the 3DS in a move analysts say is a sure sign it's worried about wooing consumers.
Kamide says Nintendo is likely to fall short of its sales target of 16 million 3DS by the end of the fiscal year through March 2012.
So far, Nintendo has sold just 4.32 million 3DS machines around the world.
Nintendo has ruled in portable gaming for years. It sold nearly 150 million DS machines since they went on sale in 2004, outpacing the Sony PlayStation Portable, whose cumulative global sales total 71 million.
But the gaming industry may be rapidly changing.
"It's a bit of a hard sell," Kamide said of the 3DS attachment.
Explore further: Nintendo seeks to rev up 3DS with holiday games