In the early days, the games they developed were online puzzle games but then they came up with Bloons, a game which pits a monkey with a dart against a bunch of balloons.
"When Bloons launched, it really just exploded. Bloons began in April 2007, we put the game on our site and it got taken up early on the social network site, Digg."
In the first week it had 3 million plays and has now had 1.5 billion plays since its launch.
At the end of 2007, Bloons Tower defence was launched, another "huge success," says Chris.
It captured a different audience from Bloons, it was more boyish and appealed to strategy game players. The Bloons Tower defence series has had 750 million plays.
A crucial step in 2008 was an approach by Scottish development company Digital Goldfish to put Bloons on iPhone as an application. The Bloons app got to number two out of all the apps in the US.
"I think we have been a combination of lucky and clever," says Chris. Goldfish, which handles Bloons and Bloons Tower defence for android and iPhone, has eight to nine people dedicated to working on the Ninja Kiwi games.
Ninja Kiwis' turnover is in the sub-$10 million bracket.
"Somehow we seem to grow revenue by 50 to 70 per cent every year," says Chris.
The company's business model is revenue from its apps business, selling virtual currency and advertising revenue from the games and the website.
In December Ninja Kiwi launched its much-anticipated Bloons TD5.
"We have to hit it out of the park each time," says Chris.
Bloons TD5 was launched in conjunction with its new free site registration system which has attracted 600,000 registered users in the last two months.
"We will then build [the system] into all our future games to enable us to provide a number of useful benefits to our players such as safe storage of their save game data, access to special challenges and achievements and a personal profile page," says Chris.
Ninja Kiwi's 15 fulltime staff include six programmers and four artists, all New Zealanders.
Executive producer, American Scott Walker, has been a valuable addition since 2010. He came from EA (Electronic Arts) games, a billion dollar game company.
"Scott fills the gaps around us, he's brilliant," says Chris.
The staff include three close friends. "The strength of these relationships is one of the keys to our business," says Chris.