What is Overlay Wild?

An overlay wild is a wild symbol that the game lays on top of the grid once the reels have stopped, instead of one that arrives on the reels themselves. Mechanically the reels resolve first, the overlay is then dropped onto one or more positions, and the win is evaluated with it in place. The reason studios build features this way is control. A symbol that lives on the reel strips can only appear as often as the strip allows, and changing that frequency means changing the game's mathematics. An overlay is added afterwards, so a feature can guarantee a fixed number of wilds — three to five on every free spin, say — without touching the base reels at all. It is the usual way a free-spins round is made noticeably richer than the base game. For a player the practical points are two. First, overlay wilds are usually restricted to particular reels or a particular mode, most often free spins, and the paytable states which. Second, they are placed at random rather than paid for by a symbol combination, so no amount of reading the reels predicts them. Overlay wilds are sometimes described in studio material as random wilds, and the two overlap heavily; where they differ is that random wild is a statement about how the symbol is chosen, and overlay is a statement about how it is drawn onto the screen. A game can also give an overlay wild an extra property, such as a multiplier or the ability to expand, in which case the paytable names that behaviour separately.