Fast-casual restaurant Chipotle Mexican Grill (NYSE:CMG) has seen some impressive momentum recently as its turnaround under new CEO Brian Niccol takes hold. Investors are thrilled. Shares have surged 135% over the past 12 months.

The strength of the company's business was reinforced earlier this month when the fresh Mexican food company announced its fourth-quarter and full-year results. The quarter capped off a strong year that featured comparable-restaurant sales growth, robust digital sales, and more.

Here's a look back at some of the areas of Chipotle's business that investors have been impressed with.

Chipotle burrito, chips, and guacamole

Image source: Chipotle Mexican Grill.

1. Revenue rose 8.7%

Chipotle's revenue rose 8.7% year over year in 2018. Highlighting the company's momentum, this was on top of strong, double-digit revenue growth in 2017; Chipotle's revenue rose 14.7% in 2017.

The company benefited from both comparable-restaurant sales growth and 83 new restaurants.

2. Comparable-restaurant sales increased 4%

Chipotle's comparable-restaurant sales were up 4% year over year -- despite a tough comparison of 6.4% growth in 2017. The key metric saw particular momentum in the final quarter of the year, with comparable-restaurant sales increasing 6.1% year over year.

3. Digital sales surged 42.4%

One area in which everything seems to be going right for Chipotle is the company's digital sales. Digital sales skyrocketed 42.4% year over year in 2018, with 65.6% year-over-year growth in the fourth quarter of the year.

For the full year, digital sales impressively surpassed half a billion dollars. This meant digital sales accounted for 10.9% of the company's total revenue in 2018.

4. Restaurant-level operating margin expanded to 18.7%

Leverage from sales growth at its restaurants meant the company's operating margin expanded from 16.9% in 2017 to 18.7% in 2018.

5. Adjusted earnings per share jumped 33%

Combining Chipotle's strong revenue growth and its widened operating margin, the fast-casual food company's adjusted earnings per share increased 33% year over year in 2018 to $9.06.

6. Chipotle bought back $161 million of its own stock

Another way Chipotle boosted shareholder value in 2018 was with its share buybacks. The company spent $161 million buying back its own stock during 2018, repurchasing shares at an average price of $370 -- significantly lower than the stock's current price of about $600.

7. Expect mid-single-digit comparable-restaurant sales growth in 2019

Looking to this year, management is confident it can keep up its strong momentum. Chipotle guided for comparable-restaurant sales to increase at a mid-single-digit percentage rate year over year in 2019.

To help drive its growth, management plans to invest more in digital sales and marketing and roll out a loyalty program nationwide.

Daniel Sparks has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Chipotle Mexican Grill. The Motley Fool has a disclosure policy.