Games that use the tumbling reels format are usually set up similarly to standard machines. You’ll put in your bet, hit a button to start your spin, and if you make left-to-right matches across the screen, you’ll be awarded your winnings.

The difference is that while this is when most slots end, these games are just beginning. Once your initial earnings have been paid, all of your winning symbols will be removed from the reels, with the remaining symbols sliding down the screen as far as possible. You’ll now have some blank spaces at the top of the screen, and new symbols will fall into place.

Now that the new symbols are on the screen, the game will once again check for any wins. If you again have the right combinations of symbols, you’ll score new prizes, and the process will continue. Depending on the machine, this could go on indefinitely (until you fail to make a winning combination), or there might be a set number of times the feature can be activated before it stops. If you've played games like?Candy Crush you will recognise this feature immediately.

In many of these games, you’ll get an added bonus if you can get the screen to continue tumbling time and again. Most commonly, this is done through a multiplier on future winnings. For instance, the first respin might be for the regular coin values, but all of your winnings on a second respin might pay double, while then next one could pay 3x, and so on.

The tumbling reels feature comes with two major benefits for players. The first is that it opens up the opportunity to win big prizes even on machines that don’t initially seem to have outstanding jackpots available. Since you can continuously trigger wins again and again, it’s possible to build up a lot of small victories into one massive haul by the end of an especially lucky spin.

It’s also undeniable that this sort of bonus action adds a lot of drama and excitement to every spin. Once you’ve retriggered a set of symbols at least a couple times, you start to feel like you might be on the verge of a once-and-a-lifetime streak. This is especially true in games that add a multiplier as you get deeper into your respins, as even just one good result at a 5x or 10x multiplier can be enough to add a huge boost to your bankroll.