This restaurant chain achieved 12 years of unstoppable growth by making only 3 changes to the menu

At Wingstop, simplicity trumps all.

That means rare menu changes, minimal seating, and low costs.

This strategy is helping the company become one of the hottest chains in the business.

Wingstop increased total revenue 16.5% in the third quarter, the company reported in November. In 2015, the company is on track to post 12 consecutive years of positive same store sales growth.

"When we started 21 years ago, we sold wings, sides and fries," CEO Charlie Morrison told Business Insider. "We've had the same three sides on the menu since the beginning, we've added boneless wings over the years, and we've added two new flavors. That's innovation for us."

At Wingstop, simplicity starts with design. Wingstop says its average unit volume is $1.1 million, but that it only costs about $375,000 to build a new location because of their small size (about 1,700 square feet).

Originally, Wingstop was takeout only. Now, there is some seating for lunchtime customers, but 75% of the business is still take away. This helps protect the company from factors that damage sales at wings-centric bars such as Buffalo Wild Wings, like a shorter sports seasons, while also fulfilling more customers' orders more quickly.

The simplicity of a takeout menu makes Wingstop a prime candidate to grow digital sales. Online and mobile orders now make up about 15% of all domestic sales, more than double last year's figure.

Online orders fit into Wingstop's dedication to simplicity, as they cut out the middle man and electronically deliver requests directly to the kitchen. Currently, more than 60% of orders are made on the phone and nearly half of Wingstop customers are millennials, making the switch to increased online sales a relatively straightforward one for the chain.

"The pizza players are in the 50% plus space," Morrison says on digital sales. "I don't see any reason why we can't aspire to be up in that kind of echelon with them."

Wingstop's final promise of simplicity is the one that is most obvious to customers: the food.

"We don't want to be is all things to all people, and have 20 or 30 different flavors," says Morrison. "We just don't think that's the right strategy for this brand."

The chain has 11 wings flavors, with a new limited time offering added to the menu twice a year. There are three sides: fries, beans, and coleslaw. The most popular flavor is lemon pepper, the recipe of which has not been changed since the chain opened.

In other words, while Wingstop calls itself a fast casual chain, it isn't going to be regarded as a trendy zeitgeist like Shake Shack or Chipotle. The chain isn't really interested in new menu items, delivery, or flashy deals.

What you see is what you get - and that's serving the company just fine.