Slot machines have changed dramatically since they first arrived at the tail end of the 19th century. Early machines relied on physical reels, simple symbols, and mechanical components. Modern versions can now feature detailed animation, soundtracks, and themes inspired by pretty much anything under the sun. Each change has been closely tied to the technology available at the time.
You can see the progression through individual machines and games. Later providers such as NetEnt, Play’n GO and Big Time Gaming used software to rethink how reels, symbols and themes could work. Modern releases are certainly considerably more elaborate, but many still retain ideas and imagery that date back more than a century.
From Mechanical Reels to Video Screens
Charles Fey developed the Liberty Bell slot machine in San Francisco in the 1890s. It featured three mechanical reels with horseshoes, stars, playing-card suits, and bells. Landing three bells led to the highest payout.
Fruit images soon became an important part of the design. Cherries, lemons, and other fruits soon appeared alongside bars and bells. This style stayed popular in casinos and pubs for decades. In fact, you can still find these symbols in some new titles today.
Bally’s Money Honey, introduced during the 1960s, represented an important technological step because it combined familiar physical reels with electrical operation. Its hopper could make automatic payouts of up to 500 coins, while electrical components made lights, sounds, and other functions more prominent. The traditional lever remained at first, even though electrical operation meant it was no longer really needed.
The next big change came when physical reels disappeared altogether. Fortune Coin Company developed a video slot in 1976 using a modified Sony television, and first demonstrated the machine at the Las Vegas Hilton. Displaying reels on a screen eventually gave designers opportunities to add paylines, graphics, and features without building increasingly complicated mechanical systems.
Video Slots Added Features Beyond the Reels
The arrival of video technology did more than just replace physical reels. Once software controlled the games and displayed them on a screen, designers could add sequences that took place outside the main reel layout. These bonus rounds soon became hugely popular and provided a way to change the appearance and mechanics of a game for a brief spell.
WMS Industries helped popularise this approach during the 1990s with games such as Reel ‘Em In. Its bonus feature used a separate screen rather than keeping all of the activity on the standard reels. This type of second-screen feature later became common across video slots, giving designers more space for animation, characters, and interactive elements.
Wild and scatter symbols also became common features of digital slot design. Wilds could substitute for other symbols, while scatters could trigger bonuses or free spins without necessarily appearing on a conventional payline. Developers could then create several layers within the same game rather than relying entirely on matching symbols across a fixed line.
This period also changed the role of graphics. Mechanical machines had limited space for artwork, primarily on the cabinet and reel symbols. In contrast, video screens could display backgrounds, animated sequences, and changing visual effects. Theme and presentation became more important parts of distinguishing one release from another.
The Internet Expanded What Designers Could Do
The growth of internet casinos during the 1990s meant a slot no longer required a dedicated physical cabinet. Games could be distributed as software, while improvements in computer graphics gave studios more options for characters, backgrounds, animation and bonus features. Providers could also develop larger catalogs without manufacturing and installing a separate machine for every new release.
Internet casinos appeared in the 1990s, which meant even more freedom in design. Games could be shared as software, while improved graphics gave developers far more options for characters, backgrounds, design, and bonus features. Soon, providers could have 1,000 of titles in their catalogs, with no need to install physical machines.
The development of online slot games created more opportunities to experiment with mechanics. Traditional reels remained common because players already understood them, but there was no technical need for symbols to behave like objects attached to a rotating wheel. Developers could make them disappear, fall, expand, split, or change during a sequence.
NetEnt’s Gonzo’s Quest, released in 2010, became a great example. Instead of conventional spinning symbols, its Avalanche mechanic drops blocks into place, with symbols in a winning combination disappearing before replacements fall into the spaces they leave. This can produce another combination from the same sequence rather than requiring an entirely separate spin.
The game also placed a recognizable character at the center of its design. Gonzo is depicted as a conquistador searching for El Dorado, with stone structures, animation and music supporting the adventure theme. NetEnt later returned with Gonzo’s Quest Megaways, combining the established character and setting with another developer’s newer reel system.
NetEnt’s Starburst, released in 2012, showed that detailed storytelling wasn’t necessary for a digital title to establish a distinctive identity. It used a conventional five-reel layout but combined colorful gemstones, space-inspired visuals, electronic audio, and expanding wild symbols. The differences between Starburst and Gonzo’s Quest showed how widely presentation could vary even within one provider’s catalog.
New Mechanics Changed the Familiar Reel Layout
As online slots continued to develop, some providers focused on changing the reel structure itself. Big Time Gaming was influential with its Megaways. This system was closely tied to the slot Bonanza, which was released in 2016. Rather than showing the same number of symbols on each reel during each spin, the number can vary. This changes the number of ways to form combinations and win.
Bonanza comes with up to 117,649 ways to win and combines the variable reel structure with cascading symbols and a mining theme. The mechanics were key to the identity of the game rather than being minor additions to an otherwise standard five-reel slot. Big Time Gaming later licensed Megaways to other studios, which helped the concept spread far beyond its own titles.
Blueprint Gaming used the system in releases including Diamond Mine Megaways, while Red Tiger later combined it with an existing NetEnt property in Gonzo’s Quest Megaways. The development showed how a recognizable mechanic could become valuable intellectual property in its own right. Providers no longer differentiated releases solely through artwork and themes, as reel behavior could become a recognizable feature in its own right.
Play’n GO took a different route with Book of Dead, released in 2016. Its basic five-reel layout is more conventional, but fictional explorer Rich Wilde and the ancient Egyptian setting give the title a strong identity. The provider subsequently used the character in games including Rich Wilde and the Tome of Madness and Rich Wilde and the Shield of Athena.
Popular Culture Moved Onto the Reels
Instead of inventing new characters and themes for each title, developers soon started to lean into popular culture for inspiration. This meant films, TV programs, and musicians started appearing in slot games, making them attractive to a new audience.
Microgaming became very active in licensed games, producing titles linked to Jurassic Park and Game of Thrones. NetEnt pursued music licenses with releases featuring Guns N’ Roses, Motörhead and Jimi Hendrix. Other providers have produced slots based on everything from action films and television comedies to game shows and musicians.
Licensing changed the design challenge because simply placing a familiar name above the reels was not enough to reproduce the original property’s identity. Depending on the rights available, developers could incorporate character imagery, logos, music, video clips and other recognizable elements. Bonus sequences could also be designed around scenes, characters or ideas taken from the source material.
Music became especially significant in titles based on performers. Traditional mechanical machines produced much of their sound through their operation, including spinning reels, bells and falling coins, whereas digital games allow every piece of audio to be deliberately designed. A music-themed release can use recognized songs as part of its identity, while an original title can have a soundtrack written specifically to match its setting.
Original Games Became More Cinematic Too
A provider does not need a Hollywood or music license to create a detailed theme. Improvements in animation and graphics have allowed studios to develop original characters and fictional settings with their own visual identities
Hacksaw Gaming’s Wanted Dead or a Wild is an example of a modern release built around an original Western theme. Its artwork, characters, and bonus features work together to establish the setting rather than relying on generic playing-card or fruit symbols.
Pragmatic Play has also developed ideas seen across releases, with titles such as Sweet Bonanza using bright confectionery imagery and Big Bass Bonanza establishing a fishing theme that has since appeared across numerous related games. These series show that providers can create recognizable visual brands internally rather than relying entirely on external licenses.
Modern themes can consequently operate at numerous levels. Some games use little more than a visual setting, others develop recurring characters, and licensed releases can draw directly on established popular culture.
Smartphones Forced Designers to Think Smaller
The growth of smartphone use created another significant design challenge. A layout originally developed for a desktop monitor could become difficult to use when reduced to a small touchscreen. This was especially the case if the interface contained numerous buttons, information panels, and complicated graphics. Developers had to consider how every element would appear and function on a much smaller display.
Touch controls also changed interaction. Buttons needed to be large enough to use comfortably with a finger, text had to remain readable, and important information could not be hidden behind crowded graphics. Games also needed to adapt to different screen dimensions and, in some cases, both portrait and landscape orientations.
Providers including Play’n GO, Pragmatic Play and Hacksaw Gaming now operate in a market where mobile compatibility is a standard consideration at the start of the design process. Games such as Hacksaw’s Chaos Crew and Wanted Dead or a Wild demonstrate that detailed artwork and multiple features can still work within relatively compact interfaces. Mobile design is now considered during development rather than added after a desktop game is completed.
The move also encouraged cleaner interfaces. Information that once occupied permanent space around the reels could be moved into menus, while controls could be simplified or repositioned. The challenge became fitting increasingly complicated games onto smaller screens without making them difficult to understand or navigate.
Classic Fruit Machines Have Never Disappeared
Even after more than a century of technological development, traditional slot imagery remains common. Three-reel games still feature cherries, lemons, bells, bars and sevens, while providers continue producing releases deliberately designed to resemble older fruit machines. Digital technology has expanded the available options without eliminating the designs that came before it.
Modern providers can work at opposite ends of the design spectrum. One release might recreate a traditional fruit machine with three reels and familiar symbols, while another uses changing reel structures, animated characters, licensed music, and extensive bonus sequences. Both ultimately grew from the same basic idea: symbols forming combinations across reels.
More Than a Century of Changing Design
The journey from Liberty Bell to current digital releases has involved several distinct stages. Electromechanical technology automated functions once controlled by physical mechanisms, video screens removed the need for real reels, online distribution let software developers experiment more freely, and smartphones changed how games had to fit on a screen. Each development expanded designers’ choices without completely replacing what came before.
