One of the most important and recognisable features of online slots is the ubiquitous Wild symbol. Unlike slot machines of old, these Wild symbols do much more than simply substitute for other symbols on the board. Wild symbols in modern slots behave in all sorts of different ways.
This is the most basic type of Wild symbol. Normal wilds generally have a single function - symbol substitution. A Wild symbol will most often serve as a replacement for all other symbols except bonus-triggering scatter or bonus symbols. Other wild symbols with other properties most often will still include the symbol substitution feature.
Sticky wilds will remain on the reels for longer than one spin. Most often, sticky wilds will remain on the reels when consecutive winning spins/respins are occurring and only depart the playing area when a turn occurs without a winning combination. Other sticky wilds may remain on the reels during an entire feature, such as during a free spins round.
Other sticky symbols may remain on the reel for a predetermined amount of time. When this time period is predetermined, these are generally referred to as Countdown Wilds. However, when other factors influence the length at which a Wild symbol will remain sticky, they are generally classified as Sticky Wilds.
Expanding Wilds are wild symbols that grow in size and typically cover an entire reel when they have finished expanding. Sometimes these symbols need to land on top of another symbol to activate the expansion, but often all an expanding symbols need to trigger is simply landing in a specific reel or row.
Spreading wilds expand into adjacent reels or columns. Spreading wilds are found in a handful of main games, but these spreading wilds are usually only found in free spins or bonus features due to the fact that they tend to produce fairly large wins. Spreading wilds may expand to cover a single or multiple locations on the reels depending on the game and feature.
A Walking Wild is a wild symbol that moves its way across the reels on subsequent spins. Most often, a Walking Wild will appear in the rightmost reel and move left one column during each subsequent spin/respin. There are some games in which Walking Wilds display different mechanics, but the right-to-left single column at a time action is the most typical for this time of wild symbol.
These Wild symbols include some sort of numeric overlay that represents the number of spins/respins in which that wild symbol will remain on the playing area. The number of “countdowns” on a wild symbol is usually awarded at random and cannot be changed despite what is occurring on the reels. Some Countdown Wilds, however, may see their counter increase if certain conditions are met, typically a winning combination or the Countdown Wild coming in contact with a symbol that awards additional numbers on a wild’s counter.
Finn and the Swirly Spin is an example of a game which features wild generation. In this title, anytime a winning combination is made without the assistance of a wild symbol, a Wild symbol is generated when the winning combination is cleared from the playing area. Wild generation is a popular feature with grid-based games that use combination clearing and respins to produce the biggest wins in these games.
Combination Wild Symbols
Most Wild symbols serve a singular purpose - wild substitution for all other game symbols. Sometimes, however, a Wild symbol may serve a dual role. Combination Wild/Scatter symbols exist which can trigger a bonus game in addition to substituting for all symbols in the playing area. These combination symbols can often be found in games with a limited number of paylines of symbols where too many additional symbols would otherwise lower the RTP to an unacceptably low level.