Just days after it was launched, Wii Fit received lots of positive reviews and became a success, with critics claiming it was worth every penny.

Amazon.com had to restock Nintendo Co.’s Wii Fit on Saturday, after having sold out all the products in early May. The company announced on the product page that it was waiting for more supply from Nintendo.

Amazon.com is not the only company which sold out Wii Fit. Major online retailers such as Best Buy, Circuit City Stores Inc. and Wal-Mart Stores Inc. also did.

It seems people decided it was worth it to spend $90 on a device that helps them lose weight or simply keep in shape through games.

The package includes the Wii software disc and a balance board that measures the user’s weight and calculates his or her body mass index, before setting players on various workout routines.

After convincing people to be more active through tennis and bowling games, Nintendo’s Wii system is now even more complex, introducing users to yoga and push-ups, with the help of the Wii Balance Board.

The Wii Fit games can be split in four categories: balance games, aerobics, strength training and yoga. The games are not all available from the very beginning, but as the user keeps exercising, more games are unlocked.

The device has already proved to be very appreciated in Japan, where it has sold 2 million units since its release last year. Many game companies tried to link video games to physical activity, but it seems Nintendo is the only one to hit the jackpot with Wii Fit.

Following its release in UK late last month, Wii Fit ranked fifth in the top ten game sales for the week.