Sony Corp.’s PlayStation2 is an intriguing middle step in the evolution of video games — somewhat like the first fish to pop out legs and awkwardly scramble onto the beach.

Home video game systems have been around for almost a quarter century, from nearly forgotten pioneers such as Atari and Coleco to modern heavyweights Nintendo, Sega and Sony.

But even as these systems have grown incredibly in computing horsepower, they still aren’t used for anything more than playing games.

Industry leaders have been talking for almost a decade about using that horsepower for other tasks, ranging from loosely defined ‘interactive entertainment’ that would appeal to a broader audience than conventional video games to Web surfing and online shopping.

PlayStation2 (www.playstation.com), arriving in very limited quantities on Thursday at $299, is the first video game console created with these broader goals in mind.

When the PlayStation2 was announced in September 1999, Sony proclaimed the box was ‘designed to bring together movies, music and games to form a new world of computer entertainment.’

That’s an exciting mission statement, but I’m disappointed Sony has done nothing more than make vague promises about when and in what form the new world will arrive.

Before I explain in detail, here’s the background almost every 13-year-old boy in Japan, Europe and North America already knows by heart:

Sony entered the intensely competitive video-game business five years ago with the PlayStation, then priced at $299. Through a combination of powerful hardware, compelling software and clever marketing, PlayStation rapidly became the leading video game platform. Sony claims somewhere between one-fourth and one-third of households in the United States now own a PlayStation.

There is a huge library of PlayStation games — about 800 titles have shipped since 1995 — with new titles typically priced at $39 to $49.

Following the inevitable downward price curve of consumer electronics, the cost of PlayStation hardware has dropped steadily. Sony replaced the original PlayStation console in September with a slimmed-down model called the PS One that sells for a mere $99.

PlayStation2 is the much-anticipated successor, introduced in Japan seven months ago and set to arrive at U.S. stores this week amid considerable hype.

Due to component shortages, Sony is making only 500,000 units available Thursday instead of the 1 million promised earlier this year.

Most of these units will go to hard-core gamers who made advance reservations. Even though Sony promises to ship 100,000 units a week through the end of the year, the PlayStation2 will likely be hard to find on store shelves until after the holiday rush.

Gamers are excited about PlayStation2 because it is much more powerful than the original PlayStation, making for more realistic characters and backgrounds, faster action and better sound.

The central processor, for example, runs at 295 megahertz and crunches instructions in 128-bit chunks, while the original PlayStation’s electronic brain works with paltry 32-bit instructions.

PlayStation2 is built around a DVD drive, so the system can play DVD movies as well as game discs. In a first for video game consoles, the PlayStation2 is backward compatible — it will play the complete library of original PlayStation titles.

Given the huge success of PlayStation, it’s no surprise that Sony is getting strong support from game developers for PlayStation 2. There will be about 30 games for PlayStation2 at launch, most priced around $49, and that number should double by the end of the year.

What seems clear is that PlayStation2 at least matches the technical performance of the year-old Sega Dreamcast, the only comparable system now on the market. It’s not clear which system will provide the best gaming experience in the long run, because game developers often spend a year or two figuring out how to goose new systems to previously unseen levels of performance.

I borrowed a PlayStation2 from Sony, but could only get my hands on one game: a martial-arts fight fest called ‘Tekken Tag Tournament.’

Sure enough, the fighters moved fluidly against ultra-realistic backgrounds. I could see incredible detail in flaming torches on the wall of a dark castle, and whirling helicopter blades on a military base.

I also loaded six DVD movies into the PlayStation2, including ‘The Matrix,’ a popular sci-fi adventure with special features in its DVD version that didn’t work on some DVD players. The PlayStation2 delivered a sharp picture for all the movies, and had no trouble accessing their special features.

A sleek, five-pound black box, the PlayStation2 looks more like a DVD player than a typical video game console, and wouldn’t be out of place in a home entertainment center next to a VCR or a stereo receiver.

The only shortcoming: The PlayStation2’s hand controller isn’t laid out in a way that makes sense for watching a movie. Anyone planning to watch a lot of DVD movies on the PlayStation2 should look for an optional wireless remote control, which will be offered by several manufacturers.

For me, the bigger frustration with PlayStation2 is that I couldn’t do anything more than play games or watch DVDs. Sony hasn’t made it clear when it will transform PlayStation2 into what one company executive calls ‘the home gateway’ for electronic information and entertainment.

Dreamcast (www.sega.com), now selling for $149, comes with a modem that enables online game play with other Dreamcast owners across town or across the world. Dreamcast also comes bundled with a Web browser disc, and Sega says about one-fifth of Dreamcast owners are using the system for Internet access.

PlayStation2, in stark contrast, doesn’t come with any Internet connectivity.

In announcing PlayStation2 a year ago, Sony said it would be ‘a platform for Internet-based electronic distribution of digital content in 2001 …’ moving through ‘an Ethernet connection to a broadband network … to download data-intensive computer entertainment content to hard-disc drives to be provided by Sony.’

Translation into plain English: Sony will offer an optional network adapter for homes with high-speed cable modems or DSL phone lines, along with an optional hard disk drive for storing downloaded games.

This network could be expanded in the future to download music, movies and other forms of electronic entertainment. Because broadband networks are always ‘on,’ PlayStation2 owners could order a pay-per-view movie or hit song and have the purchase downloaded overnight. When they were done viewing or listening, the material could simply be deleted to make room for more.

But we’re now less than three months from the beginning of 2001, and Sony has yet to give any indication of when this unnamed network will arrive, or how much the network adapter and hard disk will cost.

Given the complexity of the task and the silence from Sony, I’m wondering whether the network will be delayed beyond next year.

Another interesting aspect of PlayStation2 is the presence of a 1394 port, which Sony calls by its trademarked name of i.Link and is also known as FireWire, and two USB ports. USB and 1394 are becoming nearly universal on personal computers, so PlayStation 2 could easily make use of computer peripherals such as printers, scanners, mice, digital still cameras and digital camcorders.

Plug a digital camcorder into the i.Link port of a PlayStation 2 connected to a cable modem or DSL line and you’ve got a videophone.

Adding a printer would make the PlayStation far more useful for tasks such as e-mail and online shopping.

But again Sony is silent on when it will add software support for USB and 1394.

To go back to my opening allusion, it’s as if the PlayStation is a fish that’s evolved legs but won’t use them.

What does all this mean to potential PlayStation 2 buyers?

If you’re eager to experience the latest games and you can afford $299, nothing I can say will stop you from buying the PlayStation 2 as soon as you can get your hands on one.

Everyone else should wait.

Don’t buy PlayStation 2 just because it runs DVD movies; dedicated DVD players are widely available for less than $150, and some models may hit $99 as we enter the holiday season. I expect PlayStation 2 will cost $50 to $100 less by the second half of next year and by then Sony might finally tell us how and when the hardware will become something more than just a video game system.