So you've tried everything in the Square, from ice cream "mix-ins" to falafel to blackened chicken fingers to cheddar cheese pizza.

Cheddar cheese pizza? The Italo-Brit-American creation may not be the most common alternative to Harvard's "chicken with fine herbs," and Ruggles' Pizza is still not turning a profit. But the restaurant survives at a time when many businesses in the Square are closing up shop in the face of rising rents, a narrower, younger customer base and upscale demands.

In fact, owner Jeffrey B. Starsield notes that Ruggles has continually been making "slow, steady progress" since its founding five and a half years ago.

The acquisition of a liquor license last year, after a five-year battle with the Cambridge License Commission, is the main cause of the improvement, said Starsield.

"It is a handicap to not have a liquor license in Cambridge," the owner said. "The fact that we didn't have a beer and wine license lost us a lot of potential business." He said the commission had denied the pizzeria a beer and wine license because it felt that enough businesses in the Square had such licenses already.

In addition, Starsield said, "We're in a very good location for students. We've a good, competitive product and a basic steady following." He estimated that about 60 percent of Ruggles' customers are "regulars," people who work and live around the Square, including students.

"The people who do come in, tend to come back," said John P. Eaton, co-manager of the Cambridge eatery.

The restaurant also continues to woo students with offers like Thursday's "Pizza Night," when Ruggles pledged to donate 25 percent of the day's earnings to CHANCE, a new student-run tutoring program.

Although the Ruggles in Harvard Square is still not turning a profit, Starsield said he was able to continue with the enterprise because his original pizzeria, located in Boston, has been successful enough to support the Cambridge endeavor.

"Essentially the downtown Ruggles has been supporting the one in Cambridge," Starsield said. A third branch, in another part of Boston, closed several years ago, he said.

Boston branch manager Jeffrey M. Cree said, "Business down here has always been good. So good that it's enabled us to open up new stores, including the one in Harvard Square." Cree attibuted the success of the Boston Ruggles to "our pretty strong base of regular customers, business-people or workers downtown. Tourists are seasonal and we have a fair share of those, too."

In Cambridge, however, Ruggles' struggle for solvency has not been an easy one. Starsield called Harvard Square a tricky market. "If you hit the nail on the head, so to speak, you can do very well," he said. "There are a lot of people and a lot of potential business. If you don't do it quite right, you struggle like we did in the beginning. We kind of knicked the nail instead of hitting it on the head."

How much longer will Ruggles continue its bid for survival in Harvard Square? Starsield said he received several offers to buy out his lease on the restaurant. Although "if we were made the right offer, we'd have to carefully consider," Starsield said, "We still see a future in it. As long as long as we keep satisfying customers, we'll remain in business."