Ask a player what they remember about a slot, and the answer is rarely the base game. It's the feature: the free spins round that kept retriggering, the hold-and-win board that filled up, the cascade that just kept going. Bonus features are where theme, maths and moment-to-moment excitement meet, and they're where our design team spends a disproportionate amount of time. Here's how we think about the four feature types that appear most often in our catalogue.
The job of a bonus feature
Before choosing a mechanic, we ask what the feature needs to do for the game. A good feature usually:
- Breaks up the rhythm of the base game with a distinct mode.
- Carries a meaningful share of the game's RTP, which shapes its volatility.
- Has clear, readable rules a player understands within a few seconds.
- Builds anticipation honestly, without misleading near-miss tricks.
- Fits the theme, so it feels like part of the world rather than a bolt-on.
Free spins
Free spins are the classic. Landing three or more scatter symbols awards a set number of spins at no cost, usually with something extra to make them special. On their own, plain free spins are just more base-game spins. The design work lies in the modifier.
Common modifiers include extra wilds, removed low-value symbols, sticky wilds and multipliers. In Dragon Lantern, free spins use a multiplier that steps up with each winning spin. Our math team had to balance the starting multiplier, the step size and the cap carefully: too generous and the feature swallows the RTP budget, leaving a dull base game; too stingy and the feature feels pointless.
Retriggers
Retriggers, where landing scatters during free spins awards more spins, are hugely popular because they extend the feature's best moments. They also add long tails to the win distribution, so every retrigger rule needs careful simulation.
Cascades
In a cascading (or tumbling) game, winning symbols disappear and new ones fall into their place, potentially forming new wins from a single paid spin. Neon Reef uses cascades on a 6x5 grid, with an underwater theme where winning symbols "dissolve" into bubbles.
Cascades change the maths dramatically. Each spin can now produce a chain of dependent outcomes, so exact calculation becomes impractical and we rely on large-scale simulation instead. Design decisions include:
- Whether refill symbols come from the same reel strips or a different set.
- Whether a multiplier grows with each cascade in a chain.
- Whether cascades continue between spins in a feature or reset.
Cascades also have a strong pacing effect. A game with cascades can feel generous even at medium volatility because small wins visibly build into something bigger.
Hold-and-win
Hold-and-win (also called lock-and-respin) features trigger when enough special symbols, often coins or orbs carrying values, land at once. Those symbols lock in place and the player receives a set number of respins, usually three. Each new special symbol that lands locks too and resets the respin counter. The feature ends when the respins run out, and the values are added up.
Our Outback Gold is built around this mechanic, with gold nugget symbols on a 5x4 grid. Filling all 20 positions awards the top prize. The design challenges are:
| Decision | Effect on the game |
|---|---|
| Number of symbols to trigger | Sets feature frequency |
| Value distribution on coins | Sets typical feature win |
| Land probability during respins | Controls how far features progress |
| Special coins (collect, multiply, upgrade) | Adds variety and big-win paths |
| Full-board prize | Defines the top of the distribution |
Hold-and-win is inherently high volatility, because most features end with a modest board and a few end spectacularly. That's why Outback Gold sits in the high volatility band.
Multipliers
Multipliers aren't really a feature on their own; they're an ingredient that can be added almost anywhere: on wilds, on cascades, on free spins, on hold-and-win coins. They're powerful because they multiply rather than add, which stretches the top end of the distribution very quickly.
Our rule of thumb is that multipliers should be understandable at a glance. A player should always see what multiplier is active and why. Stacking hidden multipliers from several sources might look exciting in a trailer, but it makes results feel arbitrary. In Aurora Wilds, for instance, expanding wilds carry a visible multiplier badge so players can follow exactly how a win was calculated.
Balancing the feature against the base game
Every percentage point of RTP given to a feature has to come out of somewhere else. If a free spins round carries 40% of the RTP, the base game has to run on the remaining 60%, which means fewer or smaller base wins. That's the core trade-off behind every feature design, and we explore it further in Inside Our Math Model.
We also look closely at the "disappointing feature" rate: how often a feature triggers and pays less than a certain multiple of the stake. Some low outcomes are unavoidable in a random game, but if too many features feel flat, players lose interest. Tuning often involves adding a minimum guaranteed value or a small floor to the feature.
What we avoid
- Animations that imply a player nearly won when the outcome was never close.
- Features that suggest skill or timing affects results.
- Buy-feature options in markets where they are restricted or prohibited.
- Confusing rules that only make sense after reading three help screens.
Try them yourself
Bonus features are much easier to understand by watching them play out. Every title in our games catalogue has a free-play demo, so you can trigger features without spending anything. Remember that features, like every spin in any slot online game, are random; they make games more fun, not more predictable. Our games are for players aged 18 and over. To see the rest of what we do, return to the slot online home page.
18+ only. Our games are entertainment products. If gambling stops being fun, contact Gambling Help Online on 1800 858 858 (24/7, free and confidential).