When Niccolo de Masi, chief executive at Glu Mobile, approached Kim Kardashian West with the idea to create a game based on her lifestyle and success, the celebrity wasn't easily sold--at first.

"It took six months to go from the first conversation to a signed contract. There were many stages of her and I chatting by phone," says de Masi.

Developed by Glu, Kim Kardashian: Hollywood has pulled in more than $157 million in sales since launching in 2014. In the game, users create their own avatars and compete to ascend the ranks of the Los Angeles elite. (Glu would not disclose how much of the app's royalties are collected by Kardashian West.)

The game is free to play, though users can pay to access a variety of virtual styles--from designer clothes (i.e., Balmain's Olivier Rousteing, Karl Lagerfeld) to customized makeup. De Masi says that just about 5 percent of its global users actually pay for these features.

On Thursday, the company announced its first-ever integration with makeup brand NARS Cosmetics. Players can now access the "smoky eye" or "nude lip" looks using virtual items from NARS's "Orgasm Blush" collection, among others. Terms of the deal were not disclosed, though it's worth pointing out that NARS generates sales from links in the game itself, where users can navigate to purchase products.

The success of the game so far isn't surprising, given Kardashian West's business track record. In 2006, she launched DASH, a boutique clothing store, with sisters Kourtney and Khloé Kardashian. She later co-founded ShoeDazzle, the online fashion subscription service that raised $66 million in VC funding--with contributions from Andreessen Horowitz. (It was later acquired by JustFab in 2013).

In 2015, she launched "Kimoji," the popular app that allows users access to over 500 themed emojis for $1.99. The Hollywood socialite--who, last year, Forbes estimated to have a net worth of $53 million--has also endorsed a number of beauty brands.

Betting on the rapid rise of social media

As networking apps continue to trump more traditional gaming categories on mobile, Glu is now tapping into the massive (and highly engaged) social-media followings of high-profile celebrities. The idea is to leverage their marketing power to create simple, easy-to-play interfaces that are based more on personality than on a plot line. At present, just 32 of the top 100 free apps in the Apple store are games.

Later this year, Glu will launch games about Taylor Swift and celebrity chef Gordon Ramsay. It has already produced apps with Katy Perry and Britney Spears. Collectively, the company's celebrity partners reach more than 1 billion followers on social media.

"With the brand integration, we're adding more authenticity to the product than you would have if it were pretend clothing brands," de Masi explains. "The world going mobile means you need to bring the whole world into your mobile product."

Games designed to feel like a social network

De Masi says he's trying to build "communities" within the apps. Users can take selfies on the Kendall and Kylie app, for instance, and then directly post them on Twitter or Facebook.

Not all of these ventures have been successful: Katy Perry Pop received complaints of technical glitches upon launching and presently has fewer than 65,000 likes on Facebook. The company says it's still brainstorming ways to try and improve the user experience.

"Our team had plenty of unforeseen challenges when it came to reducing load times in the game and making it a snappy experience," de Masi says. "The other mistake that we made was [not] integrating her music," he adds.

Yet Kim Kardashian: Hollywood is still going strong, thanks in large part to the celebrity's own creative direction: She approves every visual, character, and storyline on the app, and even alerts Glu Mobile to "new additions to the family," i.e., the birth of her daughter, Saint West, last December.

"So much of this game--from the outfits to hairstyles to accessories--are all inspired by looks that I love and hand selected," Kardashian West said at the time of the app's launch. "We were able to record and include so much of my natural commentary throughout the gameplay."