It's called a "loot box" - a device in video games that unlocks random rewards like changing their character's appearance or giving them more powerful weapons to use.
While that sounds like harmless, run-of-the-mill gaming, there's a worrying catch: players are often using real cash to open these virtual treasure troves.
And, just like a pokie machine, making a payment doesn't guarantee the goodies, compelling players to up their chances by spending more of their own money.
Their inclusion in games like Overwatch, FIFA 18, Madden N.F.L. 18 and Star Wars Battlefront II has already drawn sharp criticism, spurring developers to leave them out of new products.
Now Kiwi and Australian researchers who investigated loot boxes say they're "psychologically akin" to many forms of gambling - raising the question of whether anyone under the age of 18 should be allowed to play games that contain them.
Their just-published study further highlighted how playing the games resulted in people quickly developing behaviours that were driven by the hope of getting a reward.
After analysing 22 games rated as appropriate for audiences 17 years old or younger, they found nearly half met all of the psychological criteria to be considered a form of gambling.
Those included the exchange of money or valuable goods; an unknown future event determining the exchange; that chance at least partly determined the outcome; that not participating could avoid incurring losses; and that winners gained at the sole expense of losers.
On face value, the researchers wrote, "loot boxes present a number of striking similarities to real-world gambling".
But whether loot boxes should be officially considered a form of gambling threw up a raft of serious ethical and regulatory implications - namely potential R18 restrictions.
While the Belgium Gaming Commission and Australian and US regulators were already investigating whether loot boxes constitute a form of gambling, there was yet no consensus on whether they were effectively illegal gambling operations.
Regardless, parents needed to be aware some games contained gambling-like mechanisms, said co-author Dr Aaron Drummond, of Massey University's School of Psychology.
"Engaging with these mechanics could plausibly result in overspending or, some researchers suggest, even result in migration to more traditional forms of gambling."
Drummond pointed out New Zealand had more game developers per capita than any other country in the world.
"Understanding the psychological risks of mechanics such as loot boxes is essential to ensuring that the New Zealand game industry remains at the forefront of ethical and sustainable video game development."
The study comes as the World Health Organisation (WHO) has proposed including gaming addiction as an official mental health condition.
The term "gaming disorder" - described as a pattern where gaming becomes so persistent and severe that it takes "precedence over other life interests" - will be included in the WHO's 11th International Classification of Diseases.