What are tumbling reels in slots? Cascades explained with real data

Tumbling reels remove the symbols that formed a win and drop new symbols into the empty spaces. If the new symbols form another win, it pays, and the process repeats until no new win appears. All of it happens on one paid spin. Pragmatic Play describes it in Gates of Olympus as winning symbols that “vanish and new ones drop in, allowing consecutive wins on one spin”. Our slot database tracks 237 slots with tumbling reels, from eight studios.

One feature, several names

BGaming’s Gemhalla Xtreme page puts it this way: “Winning symbols disappear from the grid, and new symbols drop into their place.” Details vary. In some games only the winning symbols go; in Hacksaw’s Le Cowboy, all regular symbols of the winning type are removed.

Where tumbling reels are used

Tumbles are the engine behind most grid-based games. In our database:

• 66 of 106 cluster pays slots also tumble;
• 56 of 67 pays-anywhere slots also tumble, including Gates of Olympus and Sweet Bonanza 1000, where “eight or more of the same fruit or candy symbol” pays and “sets off tumbles”;
• 43 of 88 Megaways slots also tumble.

Tumbling reels and RTP

RTP is the share of all stakes a slot is designed to return over a very large number of spins. The studio fixes it in the game’s maths, and every chain win is already counted in that figure. A tumble is not a free extra spin on top of the RTP; it is one of the ways the game delivers the return it was designed for.

Our data shows no RTP premium for the feature. The 237 tumbling-reel slots have a median top RTP of 96.40%; all 1,207 slots in our database have a median of 96.37%. The studio matters more: Thunderkick’s tumbling games have a median of 94.22%, BGaming’s 96.75%. Check the figure your casino runs in the game’s information screen, because some studios offer lower versions; see RTP versions explained.

Multipliers that grow during a chain

What changes the feel of a tumbling game most is what happens during the chain. Many games add a multiplier that grows with each tumble:

• Power of Merlin Megaways: in free spins, “each tumble during the bonus will increase the round’s multiplier by 1x”.
• Sugar Rush: grid positions “are marked after winning tumbles”, and later wins on a marked spot add a multiplier that doubles up to 128x.
• Golden Shower: each vacated position gets a 2x multiplier that can double up to 999x.
• Gates of Olympus: multiplier symbols up to 500x land on the tumbling reels and, in free spins, add to a running total.

These features make a long chain worth far more than the same wins spread over separate spins, so a larger share of the return depends on rare, long sequences. That is why tumbling games are mostly volatile. Of the 79 with a studio volatility label, 39 are very high and 37 high. The median maximum win is 10,000x across 214 titles that publish one.

Hit frequency

Tumbling reels let a spin pay more than once, but they do not make paying spins more common. Nolimit City publishes hit frequency for its games. Its 21 tumbling-reel slots in our database have a median of 22.38%, slightly below the 24.14% median of its 96 other slots. The groups are small and differ in other ways, so this shows only that tumbles do not guarantee more frequent wins. Our hit frequency guide explains the figure.

Tumbling-reel slots on this site

88 tumbling-reel slots have a page here and a published RTP. The table lists the 20 with the highest top RTP; a dash means the studio page we record does not give the figure.

Method

A slot counts as having tumbling reels when its studio game page, as recorded in our database, describes winning symbols being removed and replaced, under any of the names above. We excluded uses of “refill” that refer to something else, such as refilling lives in a respin bonus. “Top RTP” is the highest version the studio lists; volatility and maximum win are the studio’s own labels and figures. Database-wide counts cover all 1,207 slots we track; the slot table lists only those with a page here.

A long chain of tumbles is rare by design and cannot be predicted. Set a limit before you play and treat slots as paid entertainment. If gambling stops feeling like entertainment, free help is available 24/7: 1-800-MY-RESET in the US, 0808 8020 133 in Great Britain and ConnexOntario on 1-866-531-2600.