Players of the popular mobile game Uma Musume Pretty Derby have taken to the streets in horse and buggy carriages to protest their treatment in the game, reports Korea JoongAng Daily. Specifically, they say, they’re not receiving proper notice about major events in the game and are offered fewer benefits than players in Japan, including loot boxes (opportunities for players to pay for in-game advantages).

The protests come after users won a class action suit against the Korean distributor of the game last month. Players demanded refunds of money they had spent in the game, ultimately winning approximately $142 per plaintiff.

Haven’t heard of Uma Musume Pretty Derby? It’s a game would be a hard sell to most players in the North American market. The mobile simulation game tasks players to train an uma musume—“horse daughter” in Japanese. Those are reflected on screen as young girls with horse ears and tails.

The horse and buggy protests started in August, with players piloting them through the neighborhood where the Korean distributor is located.

Loot boxes have been a hot topic item in the video game industry for many years. Consumer groups around the world (most recently in Europe) have called for regulation of the game mechanic, calling it exploitative.

They offer players the chance to get in-game items, such as weapons or power-ups, using in-game virtual currencies that can typically be obtained in two ways: hours and hours of gameplay, or paying real money to speed things up. Players don’t know what they’re getting until they pay, though, which critics have said puts loot boxes on the same level as gambling.

Korean game companies have relied heavily on loot boxes as a revenue source for years, offering access to the game for free. Other countries use a different model, where players must pay to access the game upfront.

Worldwide, loot boxes generated more than $15 billion in 2020.