Kazuyuki Okada wanted to make it simple. He picked up a clear plastic cup containing 20 dime-size discs. Each disc weighed one gram.

"This is our gram strategy," said Okada, executive officer and general manager for vehicle development of Mazda Motor Corp. He carefully removed one disc from the cup -- one at a time.

"This is what we've done wherever possible in the car," said Okada, referring to the 2006 Mazda MX-5 Miata roadster, formally introduced here last week.

"We looked at everything," Okada said. "We put our engineers in teams. Each team was responsible for reaching weight targets for different components and modules. It was like a game."

If so, it was a high-stakes game. The Miata, introduced in 1989, is a lightweight car that carries a heavy load in Mazda's global marketing plans. According to the Guinness Book of World Records -- as noted in May 2000, with 531,890 Miata cars produced and sold by that date; and again in April 2005, with 700,000 Miata models in global circulation -- the car is the best-selling two-seat convertible sports car in history.

That success begot competitors -- from BMW with its Z3 and Z4 roadsters; from Porsche with its Boxster models; and lately, from General Motors Corp., which is planning to take on the Miata with the double-barreled introduction of two roadsters, the Pontiac Solstice and the Saturn Sky.

But its current sales numbers and its lengthy and generally favorable product-development history indicate that the Miata is the standard-bearer of the segment, the roadster to beat in terms of overall appeal and affordability.

"The Miata is the soul of our company. It isn't something we decided to do this year," said James Sullivan, chairman and chief executive of Mazda North America.

That means the new edition was something Mazda had to get right -- which is a very tricky business.

There were two seemingly contradictory needs in the Miata's redevelopment. The car had to be bigger. That is because people have gotten bigger, especially in America, the global automotive industry's most lucrative market, which also is the home of McDonald's, Wendy's and Burger King.

But weight is the enemy of things light, tight and nimble -- all of the things that make a good roadster a roadster and splendid fun to drive. How do you reconcile the need to cut weight with the imperative to increase size, add more horsepower and enhance the feeling of what Mazda engineers call "Jinba Ittai," the notion that rider and horse -- or driver and car -- are one?

"You do it one gram at a time," Okada said. "Very carefully."

Grams add up -- 454 of them equal one pound. The target weight for the new base Mazda Miata MX-5 was 2,487 pounds -- only 22 pounds heavier than that of the old car with all of the improvements, including increased structural rigidity, required by the new.

Compromise here involved weight trading. Lightweight, thin-gauge, high-strength steel -- which Mazda engineers say has three times the strength of ordinary steel -- was used wherever possible. Other material substitutes -- aluminum for the hood and engine block and molded plastic for the engine's intake manifold -- also helped hold down weight. Weight savings in the new engine bay alone totaled 42.1 pounds, according to Mazda's engineers.

No feasible weight reduction -- a weight cut that could be made without undermining the safety or performance of the car -- was ignored, Okada said. For example, using a hollow tube instead of a solid rod for the front anti-roll bar -- a part of the front suspension -- saved five pounds. Redesigning the car's rearview mirror saved a fraction, 0.19 pound -- that is, 86 grams.

Weight cuts made way for things added -- more crash protection, including a hood designed to reduce fatal injuries to a pedestrian who might be struck by the car. In the end, all of the trimming, adding, rearranging and materials substitution yielded a car that feels more substantial and less toy-like than its predecessor, but that has remained light and agile on its wheels.

But Okada and Sullivan are hoping that they've done enough to keep the Miata a heavyweight in the marketplace. Although Mazda has lit up the sales charts in recent years with its "Zoom, Zoom" sports-car philosophy, it remains a company in search of multi-segment respect.

The Japanese automaker, in which America's Ford Motor Co. has a 33 percent interest, is exploring other market segments. Currently, "we're in only 49 percent of the market segments" serviced by Mazda's rivals, Sullivan said.

He and other Mazda officials attending the unveiling of the new Miata here declined to give specifics on what Mazda might try to sell next. But current market trends show consumer money rolling toward crossover, wagon-type vehicles on one end, and in the direction of luxury cars on the other.

Whichever new segment Mazda chooses to enter, Sullivan and his people want to go in as winners. At prices ranging from $20,435 to $26,700, with the new Miata, they may have the right ticket.

Some 2006 Mazda MX-5 Miata particulars:

* Front-engine, rear-wheel-drive, two-seat roadster.

* Manually operated convertible top; but lightweight and easy to operate.

* Two-liter, 16-valve, in-line four-cylinder, 170-horsepower engine (in North America).

* Standard five-speed manual transmission. A six-speed automatic that can also be operated manually is optional.

Mazda set out to keep the 2006 MX-5 Miata light and nimble -- one gram at a time -- as it made the roadster bigger for the North American market.