A Japanese cat-collecting smartphone app, which only recently become available in English, has gained a cult following here among cat lovers.

Neko Atsume: Kitty Collector, available free on iOS and Android, has won millions of fans - both here and abroad - for its simple design and cute cats.

In the game, users own a yard and are given two forms of currency - silver fish and gold fish - which can be used to buy food, toys and treats for stray cats.

The game's objective is to lure cats into the yard for users to admire and take photos of, which can then be shared on social media.

There are 48 types of cats and they come in different colours and designs. Of these, 16 are labelled "rare" cats and getting them to appear is supposedly an "end game", or at least one of the game's highlights.

Rare cats include those dressed as a chef, baseball player, samurai and one resembling Vogue editor Anna Wintour.

Although free to download, Neko Atsume is considered a "freemium" game as users can use real money to buy additional gold fish.

Launched in October last year, the game has been available in English since two months ago.

Despite it being available only in Japanese before that, it was reportedly downloaded about 5.5 million times by July.

While not as successful as Angry Birds - widely considered among the most downloaded freemium games, with reportedly more than 42 million downloads in its first year - Neko Atsume has won many fans here.

Account executive Fadzeera Fadzully, 24, who began playing two months ago, checks the app hourly while she is awake.

She says: "I get excited when I see a rare cat appear in my yard. So far, the rarest cat which has come to my yard is Mr Meowgi, who resembles a samurai."

Even those who have real cats like to play the game. Ms Tricia Lee, 41, who co-owns The Company of Cats, a cafe in Chinatown where diners can also cosy up to felines, is also a fan.

At her "most obsessive", she used to check the game every 20 minutes.

The game appeals to her "love of collecting" and "wanting to have a bunch of cats lounge around me", she adds.

"It's such a thrill to log in and find a new cat or a present that was left by a cat."

Assistant Professor of Information Systems Technology and Design Simon Lui, 34, from the Singapore University of Technology and Design, credits the app's success to its excellent interface design, integration with social media and adorable characters.

He says: "I thought this game would appeal only to young Japanese. But now, even my cousin and grandmother know how to play it."

The appeal also comes from the fact that no one loses in this game, he adds. "If you keep trying, you will get the cat you want and the promise of it happening can be quite addictive."

Assistant Professor Alex Mitchell from the National University of Singapore's Department of Communications and New Media says the game works because of its relatively relaxed approach.

He says: "Unlike other apps that require players to check in periodically, there is no penalty in this game for not checking in and no pressure to level up or maintain resources.

"Such low-pressure games have a broad appeal and I know 10-year- old girls and men over 40 - like me - who play Neko Atsume."