In order to spin the reels & hope for matching symbols that would result in payouts, players would pull a lever. These machines developed into increasingly sophisticated models with numerous paylines and elaborate themes over time, opening the sata kinghdoor for the contemporary video slots that rule casinos today. As the technology in gaming machines advanced, so did the popularity of jackpot games. The industry was completely transformed by the advent of electronic slots in the 1960s, which made it possible to create more complex designs and gameplay elements. With the introduction of progressive jackpots, in which a percentage of every wager goes toward an expanding prize fund, the temptation to strike it rich grew even stronger.