Amazon is currently making headlines with its Underground free gaming initiative, but that doesn't mean it's ignoring its more conventional business.

One such line is its new Merch program.

It's a self-service system for branded t-shirts, with Amazon using mobile game developers such as DragonVale developer Backflip and Trivia Crack studio Etermax as spokesmen for the service.

Hipster Whale's Crossy Road and Spry Fox's Alphabear are other high profile mobile games using Merch. 

Easypeasy

Simply put, developers can sign up, and design their t-shirts, with production, retailing and shipping all handled by Amazon.

For every t-shirt sold, developers gain a royalty, which increases with sales volume.

They can also promote shirts in-game across iOS, Android and Fire OS via Amazon Mobile Ads.

"We can poll our Facebook fans for t-shirt ideas on a Monday and be selling it on Wednesday. This is a ridiculously fast turn-around and lets us give our players exactly what they want," said Bryan Mashinter, Director of Backflip Studios.

You can find out more details here.