Open world games have a problem most other genres don’t face. Once the main story wraps up, the world still needs to feel alive. Studios have solved this in different ways over the years, and one solution keeps reappearing across some of the biggest titles on PS5: give the player a casino. What’s interesting isn’t the games themselves so much as what they borrow: real slot machine mechanics, paylines, bonus rounds, reel structures, rather than inventing something from scratch. For a lot of players, these in-game floors are the first place they encounter the actual rules of a slot machine, long before ever spinning a real one.
What a payline actually is
Every slot machine, virtual or real, runs on the same basic building block: a fixed or variable set of paylines, the paths across the reels a matching combination has to land on to trigger a win. Classic machines kept this simple, a single payline running straight across three reels. Modern video slots pushed that structure much further, with five-reel layouts offering anywhere from twenty fixed paylines to formats with no fixed lines at all, where a matching symbol on adjacent reels counts regardless of exact position. That structural jump, from one line to hundreds of ways to win, is the single biggest design shift in the history of the format, and it’s also the reason two slots with an identical theme can feel completely different to play. Red Dead Redemption 2 nods to the earlier end of that history: its saloon slot machines run on a basic three-reel, single-payline format that mirrors the mechanical cabinets of the era the game is set in.
How a bonus round is actually built
A payline only determines when a win triggers. What happens next, the free spins, the multiplier chains, the escalating symbols, is a separate design layer built specifically to extend a session and create a sense of build-up. Real bonus rounds are engineered around a rhythm: a trigger condition, an escalation curve, and a payout table that behaves differently once the multiplier stacks climb. Titles like Wolf Gold structure that escalation around a single recognizable feature, in that case a Money Respin round with jackpot symbols that lock in place, while cluster-pay games like Sweet Bonanza replace paylines entirely with cascading wins that chain multipliers together as symbols clear the grid. The Yakuza series, now published as Like a Dragon, recreates this rhythm closely on its in-game arcade floors, right down to escalating symbol chains and payout tables that behave the way an actual slot’s structure would.
Ways to win, not just paylines
The move away from fixed paylines went further than cluster pays. Megaways-style mechanics randomize the number of symbols on each reel every spin, which changes the total number of ways to win from one spin to the next, sometimes into the hundreds of thousands. It’s a format built specifically to make volatility, how often a game pays out small amounts versus rare large ones, feel dramatically different from spin to spin, even though the underlying RTP stays fixed by design. Volatility and RTP aren’t the same thing: RTP describes the long-run average, volatility describes how bumpy the road to that average actually is, and the two are tuned independently by designers depending on the kind of session they want a player to have, a distinction independent testing labs like eCOGRA verify before a game’s numbers ever reach a licensed platform.
The economics behind the reels
Beneath both the paylines and the bonus structure sits Return to Player, RTP, the percentage of wagered money a slot returns to players over a very large number of spins. It’s this number, not the theme or the animation, that ultimately defines how a slot behaves over time, and it’s calculated mathematically before a single reel spins for real. GTA Online’s Diamond Casino & Resort leans on this economic logic more explicitly than any other example: chips have to be bought and cashed out through in-game systems, membership perks unlock over time, and the venue anchors enough of the game’s ongoing content that anticipation around the next entry in the series runs as high as it does. That same economic instinct shows in the payout behavior of its slot floor, which echoes the same RTP logic that governs real casino slots: wins and losses balancing out across a session rather than any single spin.
Why the mechanics carry over so directly
None of these games needed a casino to work. Red Dead’s story has nothing to do with card tables, and GTA Online had years of content before the Diamond opened. That studios built these systems out so faithfully anyway says something about how well slot mechanics translate, and how familiar players already are with paylines, bonus escalation and payout rhythm before they ever load up a real one.
That familiarity carries over directly. Anyone who’s worked through Yakuza’s arcade floor or spent chips at the Diamond already understands the shape of a real slot: how a payline triggers, how a bonus round escalates, how a session balances out toward a payout. It’s the same mechanic, just wrapped in a different story.
