Chapter 4


Slot machines have their roots in three-reel mechanical games, but the large majority of slots in modern brick-and-mortar casinos are played on video screens. Online, of course, all games are on video.

Like slots with mechanical reels, video slots and online slots are easy to play. You just slide your money into the bill validator, choose how many paylines to play and how many coins to wager per line, and hit the button to spin the video reels.
Nothing is ever quite that simple, and there are important things to know before you play video or online slots:

  • As on modern games with mechanical reels, results are determined by a random number generator.
  • What you see on video screens is a user-friendly representation of the game being played on the RNG.
  • The house gets an edge because it pays winners at less than true odds.
  • Nearly all video slots have bonus events as a prime attraction.
  • Video slots put less of their overall payback on the main game than reel slots do.
  • Online slots are similar to video slots and very easy to play.



Video slot machines are the most popular games in today’s casinos – in the U.S., more people play them than reel slots, video poker, blackjack, craps or any other casino game. Such was not always the case. In the late 1980s, I walked into the Flamingo Hilton in Las Vegas on a busy Friday night. I walked the slot aisles, and the machines were packed with players. I spotted one space into the middle of a crowded row. That one space was the only video slot in the row.
Even with no other games available, customers wouldn’t play the video games.


Video Slots

It’s said that nothing in the universe above quantum level is truly random, but random number generators are close enough that players can’t discern any repeating patterns, and the long-term percentages are those you would expect from randomly occurring outcomes. Here are a few key points about the RNG:

  • Imaging was flat and low-resolution. The screens weren’t attractive.
  • Games used three video reels and came across as pale imitations of mechanical slots.
  • There was no animation nor were there sound effects and bonus events to set the games apart.
  • Players didn’t trust computers, and they thought video results could be fixed against them.

Mechanical-reel slots also are computerized, and the video slots were random in the same was as those with mechanical reels, but in those days before home computers, players weren’t tech-savvy. That all changed in the mid-to-late 1990s as video bonusing slots broke through to popularity, but along the way a number of things had to happen to break down player resistance.



1975: Fortune Coin Company introduces the Fortune Coin video slot, the first slot machine played on a video screen.

1979: SIRCOMA rolls out its first video poker game, promoted by its founder, Si Redd. Video poker becomes the first video game widely accepted by casino players, and sets the stage for later video breakthroughs. SIRCOMA later became International Game Technology, a worldwide leader in slot manufacturing.

1994: Bally Techologies introduces the Bally Game Maker, the first machine in casinos to put multiple games on the same unit. All were on video, to be launched by touching on icon on the screen. The most popular games were video poker and video blackjack, but video slot games also carved out a following – rare for the time.

Video Poker


Mid-1990s: Aristocrat Technologies in Australia devises games with five reels and bonus events – mostly free-spin bonuses. They weren’t an immediate hit in the U.S., but success on the Pacific Rim inspired U.S. gamemakers to start work on their own video bonusing slots.

1996: Silicon Gaming gives sneak previews of its Odyssey video slot machines. Odyssey was a high-tech marvel, with an oversized screen, high-quality animation and some bonus features. It was hailed as the future of gaming, but ultimately lost in the marketplace.

1997: WMS Gaming rolls out Reel ’Em In, the first big video slot hit in the U.S.


The success of Reel ’Em In served notice to other gamemakers that they’d have to go video if they were going to keep up with a shifting market. For the next several years, three-reel games remained the most popular U.S. slots, but innovations from multiple manufactures helped video slots built momentum. Among the important pieces that fell into place for video gaming were:


Aristocrat was the pioneer with its Hyperlink games, first popular on the Pacific Rim and later in the United States with the debut of Cash Express. Today, many manufacturers produce games with progressive jackpots
that range from a few dollars for frequent hits to build player interest on up to hundreds, or thousands, of dollars.




Players win together or lose together on banks of machines. A.C. Coin was first with Road Rally in the late 1980s, but it was the early 2000s until community-style gaming really took off with IGT’s Wheel of Fortune Super Spin and WMS Gaming’s Monopoly Big Event.


Early video slots had a single bonus event. Today, many machines have both free spin and pick’em bonuses, and some variations on those themes with six or more different bonuses so there’s always something new to anticipate.

Pop culture theme


If a theme appeals to the slot-playing demographic and it has elements that can be tied to bonus events, you can bet somebody’s trying to negotiate a license. The Twilight Zone (IGT), Lord of the Rings (WMS), Michael Jackson (Bally) The Big Bang Theory (Aristocrat) and many, many more themes have become successful video slots, or online slot games.


What would Aristocrat’s slot based on the 1960s Batman TV series be without clips and characters from the show?
What would Konami’s Neo Contra be if you couldn’t hear and practically feel that helicopter overhead? A multidimensional entertainment experience brings players to the video slots.


Special chairs accompany highly promoted games with popular themes. The chairs move, shake, rock and roll, and have speakers in the back for surround sound. The pioneer was WMS with Top Gun, where you feel like you’re in the jet fighter’s pilot seat as you target bonuses.


Video slots are casinos’ most popular games, and penny slots are the most popular video slots. To make it worthwhile for casinos to offer them, almost all have 20 or more paylines, with 40 being a common number. Without multiple paylines, and without ticket printers for payouts so machines don’t actually have to dispense pennies, there would be no 1-cent slots. The goal has been to make video slots more entertaining, and often more interactive, than three-reel slots. Though three-reel slots now often incorporate bonus events, the entertainment value traditionally has come in watching the reels to see if you win or lose. In video slots, there is entertainment value in playing the games, in launching the video clips or making choices in bonus events. You still win or lose, but gamemakers and casino operators want you to remember the fun and keep coming back even if you lose.

Key Takeaways
  • Video slots have been around since the 1970s, but didn’t really take off in popularity until the late 1990s.
  • Success of video slots on the Pacific Rim encouraged U.S. slot manufacturers to develop their own games.
  • Today, video slots put an emphasis on entertainment and interactivity, regardless of whether you win or lose.



At their cores, modern slots with mechanical reels and video slots work in the same way. Numbers selected by a random number generator and translated into the symbols you see on the reels. However, there are some important differences:

  • Video reel strips take no space and can be as long as a programmer needs.
  • Video slots almost always have more paylines than mechanical-reel slots.
  • Video slots have more winning combinations than mechanical-reel slots.
  • Nearly all video slots include bonus events, which must be accounted for in game math.

Let’s look at an example of a five-reel video slot pay table, a 20-payline game that accepts wagers of up to five coins per line:

Combination Table

This is a very basic game compared to those you’ll actually see in a casino. Most have many more potential combinations, often with A-K-Q-J-10 symbols in addition to character symbols. The maximum wager here is 100 coins, but you’ll often see 300, 400 or 500-coin maxes on casino slots. There is only one bonus event here, and many video slots have multiple bonuses.

Still, there are some things of note on this pay table that are common on video slots:

  • You don’t need to have a winning symbol on every reel.
  • Some winning spins pay less than your bet.
  • Payoffs are proportionate to bet size, with no bonus for betting the max.

All of those things are important to the video slot experience. On five-reel video slots, you don’t need the winning symbol on every reel. You’ll get some return for lining up a symbol on reels 1, 2 and 3, with bigger payoffs if you also have that symbol on the same payline on reels 4 and 5.

On some games, top-paying symbols even bring a small return with only two across starting from the left, such as on the sample game here where two hawks brings back five coins for a one-coin bet on an active payline.

You’ll also see on the pay table above several winning combinations that pay less than your bet. If you bet one coin on each of the 20 paylines for a 20-coin bet, two hawks or three mice bring five coins, and three raccoons bring 15.

That enables designers to give us games with very high hit frequencies. Some video slots have paybacks on more than 50 percent of spins, but such a high percentage of them are less-than-bet pays that they don’t lead to an unusually high payback percentage.



The multiple paylines also are important to the experience. It’s possible to have winners on more than one payline, and even have the same symbols pay on multiple lines. Let’s say four of our paylines look like this:

Multiple Payline
Multiple Payline 2


Now let’s say what we see on the reels is this:


Then on the first three payline samples above, you have two Hawks, and on the fourth you have four mice. You get the five-coin two-hawk payoff three times and the 15-coin four-mouse payoff once. In that example, your 20-coin bet at one coin per line brings a total of a 30-coin return. Those multiple pays have to be accounted for in the math of the games and the random number sets designers and programmers use. There are other factors to be taken into account, including these:

  • Wild symbols and expanding wilds.
  • Scatter pays.
  • Bonus events.



Wild symbols are matches for any symbol, usually excluding scatter symbols or bonus symbols. Let’s say that in the above example, the mouse on the third reel was a wild symbol instead, as follows:
In that case, the mouse pays remain intact, but now you have four hawks on the payline that looks like this:

Wild Symbol-Payline
Wild Symbol-Reel




Instead of a five-credit pay for two hawks, that’s a 250-credit pay for four hawks. With expanding wilds, when a wild symbol lands on the payline, it grows to fill all three spaces in a column. Let’s try putting two wilds in the above example:

Wild Wild Reels

With expanding wilds, the symbols would grow so your screen looked like this:

Wild Wild Wild Reels




Scatter pays do not have to line up on any particular payline. On many games, bonus symbols are scatter symbols, so that if you get three of them anywhere on the reels, you launch a bonus event.
Other games use scatter symbols for payoffs without going into a bonus. Let’s say our game builds in a treasure chest symbol that pays 100 coins if you get three of them, 250 for four or 1,000 for five. Then you can get a 100-coin pay that looks like this:

Scatter pay

The treasure chest spaces would not constitute a winning combination with other symbols. They do not line up on a left-to-right payline, starting at reel No. 1. But with scatter pays, having enough symbols triggers a payoff, no matter where they land.



We’ll look much more closely on bonus events later in this guide. Bonuses can be free spins, pick-a-prize events, wheel spins and more.

Their effect has to be accounted for in game math and random number sets.
One gamemaker told me that on his company’s games, about a third of payback comes from bonuses. So a game that returns 90 percent returns only 60 percent to players on the base game, but adds 30 percent on bonuses.
That can differ from game to game and manufacturer to manufacturer, but it must be accounted for by game designers and programmers.

With so many possibilities available, designers must work with large number sets.
Because the reel s and symbols don’t exist in a physical sense, there is no need to keep reel strips small enough to fit inside the machine casing. If the programmer needs the reel strip to be 100, 500, 1,000 or any other number of symbols long to yield the optimal number of combinations leading to the desired game odds, that can be done.

With five reels and large numbers, the number of potential combinations gets very large, very fast.
If each of five reel strips has 100 symbols, then the number of possible combinations for each payline is 100x100x100x100x100.
That’s 10 billion possibilities – plenty to work with while dealing with multiple wins per play, scatter pays, bonuses, expanding wilds and all the tools available to a video slot designer.

Key Takeaways
  • Video slot results are determined by a random number generator.
  • Bonuses, scatter pays, wild symbols and multiple paylines open new possibilities for game designers.
  • Game designers work with very large number sets to account for all the possibilities opened by game features.



Slot machines payoffs traditionally have been built around paylines. On three reel mechanical games, the most common configuration has been one line down the center:

Payline Basic


When five-reel video slots rose to popularity in the 1990s, the breakthrough games had five paylines, with three horizontal lines, a “V” and a chevron:

Five Paylines


That concept has grown, and as we saw in Chapter 4.2, some paylines zig and zag across the reels, such as this:

Payline ZigZag


Today, 20-, 25-, 30- and 40-payline games all are common.


Do Multiple Payline


Having all those paylines accomplishes a number of things:

  • It opens the possibility on of winning on more than one line on a single spin.
  • It gives game designers a great deal of leeway in devising games of different volatility.
  • It makes it easy to devise games with high hit frequencies.
  • It gives players a wide range of betting possibilities.

Winning on more than one line on the same spin was discussed in Chapter 4.2. The potential for games of widely differing volatility is available because there are so many possibilities in a five-reel game.

If the programmer and designer are working with 100 random numbers per reel, there are 1 billion possible five-reel combinations. High, low or in-between portions can be winners. Very frequent small wins can yield a low-volatility game that keeps you in your seat for extended play. Putting more of the return into bonuses or bigger pays can yield higher volatility with a better shot at bigger wins, but also a better shot at a faster drain on your bankroll. Players have the opportunity to choose how much to bet per payline, and on many games also can choose how many lines to play.

When video slots made their breakthrough with five paylines, button panels offered options like this, along with a large “maximum bet” button to one side:
Panel 1


In that configuration, you could bet anywhere from one coin per spin to 25. Many games with more paylines also offer betting options all the way down to a single coin, although not all coin-line combinations are offered.
Here’s one from a 20-line game:

Panel 2


Such configurations worked well when video slots first broke through. They were most commonly in five-cent, or nickel, denominations, so the least anyone was going to bet was five cents, and most players were covering all the paylines to bet at least 25 cents. When penny slots rose to popularity in the 2000s and the minimum bet became just one cent, casino operators wanted to make sure players were betting enough to keep the games profitable. That led gamemakers to devise what’s known in the industry as a “forced bet” machine.

On a 40-line, forced bet game, the button panel might look like this:
The “Bet 40” option is simply covering all the paylines at one coin per line. On such games, you can no longer bet just one coin, but you can bet one coin per payline.

Panel 3




We’ll look more closely at whether you should cover all the paylines, bet one coin per line, bet the max or bet something in between in Chapter 8: Maximizing payouts.

But here are some basics you should understand about multiline video slots:

  • On nearly all video slots, including online slots, payouts are proportionate to the number of coins wagered per line.
  • Winning combinations are equally likely to land on any payline.
  • Larger bets for covering all paylines are balanced by more frequent wins.

Here’s an example of how it works:

  • On a hypothetical 20-line machine, three “10” symbols bring a five-coin payoff.
  • Odds of the game are set so the three 10s occur one per 100 plays for each payline.
  • If you bet only one coin on one payline, each three-10s win pays five times as much as your bet, but occurs only once per 100 plays.
  • If you bet one coin on each of the 20 paylines, a three-10s pay of five coins pays one-fourth as much as your 20-coin bet.
  • However, by betting all lines, you collect 20 three-10s pays per 100 spins instead of only one.

It balances out. By betting one coin per line, you wager 100 coins per 100 spins. You will collect five coins the one time you get three 10s. One five-coin payoff per 100 coins wagered reduces to one coin collected per 20 wagered.
By betting one coin for each of 20 lines, in 100 spins you bet 2,000 coins. You collect the five-coin pay 20 times per 100 spins, meaning the three-10s are paying you 100 coins per 2,000 wagered. That also reduces to one coin collected per 20 wagered, the same as if you were betting only one coin.



In Chapter 4.2, we saw that some games use scatter symbols, in which you’re paid anytime three or more appear anywhere on the reels. Most wins still require lining up matching symbols from left to right.

Aristocrat Technologies took something very close to the scatter concept and applied to entire games. The concept is called “Reel Power” and has proved so popular that nearly all slot manufacturers have rolled out their own versions of no-paylinegames. In Reel Power games, your bets buy reels instead of paylines. Unlike scatter pays, winning symbols must appear on adjacent reels from left to right. Unlike games with traditional paylines, Reel Power winners can appear in any position on the reels. If you buy fewer than five reels, winning symbols may appear in any positions on the bought reels, plus you can win on a center payline.

If you buy just one reel, your potential winners look like this:

Payline One Reel

Potential winners with two reels bought:

Payline Two Reel


With three reels bought:

Payline Three Reel

And with four reels bought:

Payline Four reel


With five reels bought, winners must appear on adjacent reels right to left, but can be in any reel position. Take this example:

Payline Five Reel


On most games, the hawks in that configuration would not form a payline. However, in Reel Power games, as long as the winning symbols are on adjacent reels, left to right across the screen, it doesn’t matter whether the symbols are in the top, middle or bottom positions. Such games yield 243 possible ways to win, and games from gamemakers other than Aristocrat are commonly called 243 ways to win games rather than Reel Power. Reel Power games typically use free spins as a bonus event, and are among the most volatile video slots.
One offshoot is games with reels that are four symbols deep instead of three such as this:

Aristocrat calls such games Xtra Reel Power. They have 1,024 ways to win, and with so many possibilities typically are even more volatile than Reel Power games.

Xtra Reel Power




Cascading reels games use traditional paylines, but the presentation turns each slot symbol into an individual tile. When a winning combination appears, you’re paid the corresponding amount. Then, without you having to make another bet, the winning symbols disappear, and different symbols cascade down into their places.
Let’s try an example:

Cascading Reel 1

We’ll define our paylines in this one so that the first three mouse symbols are on a winning line. After you’re paid, the three mice disappear. The hawk symbol on the third reel drops down to replace the mouse, a new symbol appears above it, and two new symbols replace the first two mice.

Now if we have a fairly common payline that includes the top of reel 1, the middle symbols on reels 2, 3 and 4, and the top symbol on reel 5, we have a nice payoff on four hawks. They disappear, and symbols cascade again.

This time, there are no winners, so the play ends. Now you have to bet again to get a fresh cascade.
As long as the cascading symbols keep forming winners, you keep collecting credits and new symbols keep dropping into place.
Wins that start small can get quite large. Naturally, there’s a tradeoff in a higher percentage of losing spins than on many video slots, so cascading reels games are more volatile than many other video slots.

Key Takeaways
  • Multiple paylines give players a wide range of betting options, though some games now require you to cover all paylines.
  • Winning symbols are equally likely to appear on any payline.
  • Reel Power games, with 243 ways to win, don’t require winning symbols to line up on traditional paylines.
  • With cascading reels, each winner brings new opportunities to win.
Cascading Reel 2



At their very core, hit frequencies and payback percentages work the same way on video slots and online slots as they do on mechanical-reel slots.

  • Hit frequency is the proportion of spins that pay money to players.
  • Payback percentage is the proportion of wagers returned to players as winnings.
  • Games with high hit frequencies can have payback percentages higher, lower or about the same as games with low hit frequencies.

If there are sufficient returns in high-paying combinations, a game that give players a lower percentage of winning spins can have a higher payback percentage than a game with more winning spins that puts most of its returns in low-paying hands.



On video slots, casino industry professionals make a distinction between “entertainment” games and “gambling” games.

  • Entertainment games have high hit frequencies but low jackpot probabilities.
  • Entertainment games are designed to give players extended play.
  • Gambling games offer enhanced chances at big payoffs, but have low hit frequencies.
  • On gambling games, you can lose money faster when the big wins don’t come.

For a look at the arithmetic of hit frequencies and payback percentages, see Chapter 3.2, Hit Frequency vs. Payback Percentage. The examples are for three-reel slots, but the principles are the same. However, there are some special factors that apply to video slots.

  • Video slots and online slots have many more potential paying combinations.
  • Only about two-thirds of overall payout is on the main game, though that varies by game and gamemaker.
  • Bonus events must factor into both hit frequency and payback percentage.




We saw that video slots have more potential paying combinations with this game in Chapter 4.2, Video Slots and the Random Number Generator:

Changing hit frequency table

That is a simplified game. Most video slots in casinos will add extra low-paying symbols such as A, K, Q, J, 10. There are ways to make this a high hit frequency game, but not necessarily a high payer. Let’s do a little arithmetic for a single payline.

  • The numbers of mice could be enhanced on the first three reels.
  • There could then be fewer mice on reels 4 and 5.
  • The numbers of hawks could be increase on the first two reels.
  • There could then be fewer hawks on other reels.

You could do the same with other symbols. The key is that there does not have to be the same number of each symbol on each reel. Let’s say we’re working with 30 symbols per reel – a small number compared to most video slots.

  • There are 2.43 million total five-reel combinations.
  • There is a payoff for hawks on the first two reels. There are 900 two-reel combinations.
  • If there are five hawks on the first reel and four on the second, there are 20 two- hawk combinations.
  • You would get a payoff on two or more hawks once per 45 spins.
Hit Frequency Reel


Game designers can work with a low payoff like that once per 45 spins. But they can’t have big payoffs on five hawks coming up too often. So they can put fewer on subsequent reels. If there are five hawks on the first reel, four on the second, three on third, two on the fourth and one on the fifth, there are 120 five hawk combinations. With 2.43 million five-reel possibilities, that would give you the top payout only once per 20,250 plays.
What if game designers wanted a game with a lower hit frequency, but a game with a better chance at the biggest jackpot?

  • If there are two hawks on the first reel and three on the second, there are only six two-hawk combos.
  • The only two-symbol payer on the game now appears only once per 150 plays.
  • If we then put three hawks on the third and fourth reels and five on the fifth, there are 270 five-hawk combos.
  • The top jackpot now pays once per 9,000 plays.



On the example above, we haven’t changed the pay table at all. We’ve just changed the hit frequency on a low-paying winner by changing the number of hawks on the first two reels.

Gambling vs entertainment

The difference is subtle, but in casinos, you’ll find games with much larger differences.

  • Games with large jackpots often, though not always, are low hit frequency “gambling” games.
  • Games that use stacked symbols, where you can have big wins on many lines at once, usually are gambling games.
  • Games that have free spin bonuses as their main or only bonus event often are gambling games.
  • Games that have pick’em bonuses as their main or only bonus event usually are entertainment games.

You can use big jackpots, stacked symbols and type of bonus events as guides to what the play experience is likely to be, but those aren’t hard and fast rules. As with any slot machine, if a game isn’t meeting your expectations, you can always move to a different game.

Key Takeaways
  • Hit frequency does not necessarily correspond to payback percentage.
  • Hit frequency can be increased or decreased by changing the proportion of symbols on the video reels.
  • Casinos offer both high hit frequency “entertainment” games and low hit frequency “gambling” games.
  • Bigger jackpots, stacked symbols and free spins are among the tools that can be used to create gambling games.
  • High hit frequency and pick’em bonuses are among the tools that can be used to create entertainment games.



Casinos don’t have to replace entire machines to change games.
Only the software needs to be changed.

For the most part, slot games are chip-based. To change a game, it’s necessary to change a chip. Regulations and procedures differ from state to state and jurisdiction to jurisdiction, but basically changing a game looks like this:

  • Under gaming board supervision, a casino employee unlocks and opens the slot machine door.
  • The central processing unit is removed, the door relocked, and the CPU is taken to the back shop.
  • Evidence tape is broken, and the game chip is removed.
  • A new game chip is inserted a resealed with evidence tape.
  • The CPU is placed back in the machine, the door locked and the game restarted.


Player questions about whether slot payback percentages are routinely changed day to night or weekday to weekend are rendered moot. Changing one game is time- consuming. Routinely changing a floor full of slots costs too much in both time and money to be worthwhile.

One solution that has been explored is server-based gaming, where it’s possible to upload games onto a hard drive from a remote location. Server-based games are in use in some casinos. However, not all have the infrastructure to support the devices, and they are more costly than other machines. Combined, that’s made a transition to server-based slots a slow process.

For casinos that have the infrastructure and are willing to bear the startup costs, there are several pluses for server-based gaming:

  • It takes much less time to change a game.
  • It is possible to change games on multiple machines, even on large sections of the floor, all at once.
  • Games can be put on a timer to automatically change to fill casino needs.
  • Server-based units enable two-way communication between the casino and its players.
  • Casinos can use server-based technology to bring players targeted bonuses.

Let’s look at each of those points:



Operators and regulators, working together, can use a point-and-click method to choose games and paybacks at the click of a mouse. It can be done in seconds.

Automatic change


This does not yet appear to be in use in the U.S., but server-based games have the capability to change according to specific casino needs.

If a casino finds it draws large numbers of video poker players in the daytime, but needs more multiline penny slots at night, it can set the system up to change at a specified time each day.

All this would require regulatory approval. One thing regulators I’ve spoken with have said they will not approve is any automatic change in payback percentages. Any casino that wanted to offer 92-percent games as an attraction in low-traffic times but drop to 85 percent on busy weekends would be blocked by regulators.


The operator, with regulatory approval, can define multiple machines, whole banks of machines or even specific machines scattered throughout the casino to all change at once. Once the group is defined, the same click on game and paybacks can change them all.


Through applications such as Bally’s iDeck, IGT’s Service Window, and Aristocrat’s Media Window, players and the casino can reach out to each other. In casinos where such applications are activated, players can use them to:

**Order beverages from the cocktail server.
**Check and redeem player rewards points.
**Get restaurant information and check reservations.
**Make hotel or show reservations.
**Check on other casino services, such as spas, golf reservations and more.

The casino also can message the player, either automatically or through an operator. Among the things casinos can do are:

**Offer rewards based on player history.
**Offer extra comps when venues aren’t full.
**Offer special games and tournaments.

For example, if show time is near and a lot of tickets are unsold, the system can scan the records of active players to identify those who are closest to qualifying for complimentary tickets.

The window then can open to offer tickets, and the player can accept or decline. There’s the potential to build good will by offering comps to players who wouldn’t normally qualify, while raising no cost to the casino since the seat would otherwise be unfilled, producing no revenue. Special games and tournaments can enhance the regular game experience.



It could be as simple as once you’ve hit a wagering target amount, you get a special spin or a pick-a-prize bonus delivered to your iDeck. Alternatively, hitting that target could add a tournament display, and for the next several minutes your win totals are matched against those of other qualified players. Top finishers get an extra prize. Not all casinos use server-based games, and not all of those that do have them use such applications. Manufacturers hope they become popular and widespread, but the marketplace will decide.


Delivering Games


The situation is not as simple as a game supplier sending a game directly to a machine. That wouldn’t meet regulatory concerns. Instead, games are often sent to regulatory bodies first, who then relay them to casinos. Every jurisdiction has its own regulations, but here’s an example from the state of Indiana as to how it works:

  • The casino subscribes to monthly game updates from the manufacturer.
  • Games are put on a disc, which then is delivered to the gaming board.
  • After the disc has been approved, it is delivered to the casino and installed in its server room.
  • In the server room, a double-lock system is used.
  • Both a casino employee and a gaming board agent must be logged in to load games onto machines.

The double lock system prevents the nightmare scenario raised by players in which casinos change games and paybacks willy-nilly, without supervision. Every change must be gaming-board approved.



Even on games that are not remotely delivered, networking the machines has opened new possibilities for interactivity and for bringing the experience to players in their homes between casino visits. WMS Gaming, now part of Scientific Games, has been a pioneer with its Star Trek and Lord of the Rings slots. Such networked games are set up so that:

  • Players create an identity when they play.
  • During game play, players unlock new bonus packages and graphics.
  • The next time they play, they can log in and pick up where they left off.
  • At home, players can log onto a free play site, interact with other players and game designers.
  • During free play, players also can unlock bonus features that will be available on their next casino trip.
  • Players also can earn badges they can display to their online friends.

Star Trek and Lord of the Rings both were popular, well-received games, but this remains a small segment of video games. It has promise as more players who were raised in the social media age start to play in casinos.

Network games


Key Takeaways
  • Server-based slots can dramatically reduce the time it takes to change slot game.
  • All changes must be made with regulatory approval.
  • Server-based systems open new possibilities for bonuses and communication with players.
  • Networked games offer unlockable bonuses and the opportunity to extend the experience at home.



  1. Why did players reject early video slots?
  2. True or false: U.S. manufacturers led the world into accepting video slots.
  3. What determines the results on video slot machines?
  4. Wild symbols can substitute for: A. Any symbol. B. Any symbol except for scatter and bonus symbols. C. Only the lowest-paying symbols.
  5. True or false: Having multiple paylines increases a machine’s hit frequency.
  6. What does a “forced bet” machine do?
  7. What do gamemakers and casino operators mean by “gambling games” and “entertainment games”?
  8. Do high hit frequency games have high payback percentages?
  9. On server-based games, can operators change games by themselves?
  10. If you unlock a bonus package on a networked game, how can you keep the package unlocked when you next play?


  1. Players rejected early video slots because graphics were flat, there were no exciting extras and players not yet used to home computers didn’t trust them.
  2. False. U.S. manufacturers did not lead the world into accepting video slots. In fact, U.S. gamemakers were encouraged to produce video slots by the success such games had on the Pacific Rim.
  3. Just as on reel-spinning games, video slot results are determined by random number generators.
  4. B. On most machines, wild symbols can substitute for any symbol except scatter and bonus symbols.
  5. True. You will have more winning spins when you bet multiple paylines, but that doesn’t increase the payback percentage.
  6. “Forced bet” machines require you to bet all the paylines, so that on a 40-line game you must bet at least 40 credits, or one per line.
  7. Gambling games offer greater chances for big wins, but less return on small wins for a win big or lose fast experience. Entertainment games have frequent small payouts but a lesser chance on big wins, extending playing time for those playing for entertainment.
  8. High hit frequency games do not necessarily have high payback percentages. Games with wildly different hit frequencies can have similar payback percentages.
  9. No, operators can’t change games quickly by themselves. All changes require regulatory supervision.
  10. On networked games, any bonus packages you unlock remain unlocked for future play provided you create an onscreen identity and log in.

Written by 


For nearly 25 years, John Grochowski has been one of the most prolific gaming writers in the United States. He’s been ranked ninth by GamblingSites among the top 11 gambling experts at Gambling Sites and his Video Poker Answer Book was ranked eighth among the best gambling books of all time.