After coming off a stellar year with the top grossing title of the year in the iOS store, the big question for Sequoia Capital-backed Pocket Gems is — what’s next?

The company has rather quietly launched a host of titles in the last two months including Zombie Takeover and Tappily Ever After, as it looks to duplicate the success of its biggest hit Tap Zoo amid a more competitive environment. In the last three months, the company has released six games that range from brand new intellectual property like Zombie Takeover to seasonal releases of hits like Tap Zoo.

“You’ll see us push the envelope this year with new genres and types of gameplay,” chief operating officer Ben Liu tells us. “We have a couple big launches in the next few months.”

The company just crossed 60 million downloads. That’s not the absolute highest range for mobile game developers, but it is notable in light of how well Pocket Gems’ games ranked on the grossing charts last year. Tap Zoo alone has been downloaded more than 23 million times, while its sequel Tap Zoo 2 was downloaded by 1 million players in its launch week.

Now with 110 employees, the pressure is on Pocket Gems to see whether it can reproduce its earlier success. While all gaming companies face this challenge in a hits-driven business, it’s becoming more difficult for everyone as the charts have become more volatile in recent months. In its earnings call yesterday, Glu Mobile said that the period of peak earnings for games is shortening.

One of Pocket Gems’ recent titles is in the familar animal care-taking genre, but it has more of a storyline. In Tappily Ever After, players have to save a princess who was kidnapped on the eve of her wedding. To get to her fairytale wedding, they have to make an animal park to tame the kidnapper’s creatures.

But the company’s also moving into new territory with titles like Zombie Takeover. In the game, the player gets control of a zombie school. Using a similar mechanic as in Tap Pet Hotel, they have to go build rooms to attract specific characters then turn them into zombies. They also have to produce food to grow a zombie army, which they can then use to attack nearby buildings. Pocket Gems also did a number of seasonal titles like Tap Zoo: Santa’s Quest and Holiday Hotel.

Pocket Gems is also now facing off with one of the most formidable competitors in the app store — Zynga. The company launched Dream Zoo late last year, and then used its acquisition of New York-based Astro Ape Studios to produce Dream PetHouse. Both games are notably similar to Pocket Gems’ most lucrative titles, Tap Zoo and Tap Pet Hotel.

“We respect Zynga a lot. They have really talented developers but they’re just one company out of millions in the app store,” Liu said. “Consumers are going to judge what’s a good product and what’s not.”

Because of all the competition, Pocket Gems’ games are not quite as highly ranked as they were in mid-2011. That said, the number of iOS devices out on the market is increasing and any given ranking today on the top-grossing charts produces more revenue than it did half a year ago.

“On the whole, it balances out well for us,” Liu said. “We’re still going to do genre-defining games. And financially, we’re doing great.”