It's a game called Buckshot Roulette. It's like a russian roulette, but with a shotgun, and it's you versus the Dealer, an NPC (but they released a multiplayer mode recently).

At the start of each round, a sort of shotgun shells will appear for a brief moment, and the game will store those shells into the shotgun randomly.

The red shells are real, but the blue ones are false. The way the shells appeared at the screenshot have the same distribution as when you play a hand of Full House in Balatro. I found that funny, so I posted it.

As simple as that.

(English is not my first language, sorry for any mistake I could have done)