In a casino where players have an often-overwhelming assortment of games, attractive themes and designs are what keep them coming back for more. And, despite all the changes in technology and player tastes over the years, slot machines remain the single biggest revenue generator for casinos.

In the early days of slot machines, Charles Fey’s machine allowed automatic payouts and used three reels instead of five. It also introduced symbols such as diamonds, hearts, horseshoes, and Liberty Bells—the latter being the most lucrative—making it easier to hit jackpots. This made the machine more popular than previous variations that required a person to pull a lever to spin the reels and hope for a win.

Today’s slot designers have even more data to work with as they seek to understand what makes a game succeed. According to ReelMetrics, a company that analyzes slot machine data, successful slots have “sticky” features that cause players to return frequently and play longer. The game industry’s major suppliers have responded to this new scrutiny by increasing their reliance on research and data analytics. In fact, SG recently launched its new SG Connect system to provide operator clients with valuable player behavioral insights.

Designing a slot requires a lot of considerations, including theme, mechanics and payouts. During the idea generation phase, it is important to discuss these factors broadly to ensure that no brilliant ideas slip through the cracks. After that, market research, user testing and feasibility studies are essential to determine whether your slot has a chance of success. Then, it’s time to begin the development process. Unit testing each component of the slot is a great place to start. Once the individual components have been tested, they are combined into a working whole and subjected to comprehensive systems testing.