Designing a Gambling Game

A gambling game has five distinct elements: the house, the equipment, the mechanic, the odds, and the payout.

House: The house is the source of the game, and determines the game’s style. A “tight” house runs games where the house edge is higher, and where player influence is minimized. A “loose” house wants much more gambling to occur, and is willing to maximize its risks so that players will bet more. The standard deviation of loss or gain is higher if the house is loose. As long as the house has an advantage in all games, the other important number the house must care about is its exposure, which is how much it can lose if everyone suddenly wins at once. A house that can’t cover all its bets won’t be successful for long.

Equipment: This is what you need to play the game. It’s not just dice or cards—you often need markers, coins, and even miniatures. You should also determine how many people are necessary to run the game. Usually it’s just one dealer, but a game like craps requires four people to run it: a boxman, two base dealers, and a stickman.

Mechanic: The mechanic is how the game is played. A mechanic should be simple and easy to grasp: place a chip on the board and roll a pair of dice, choose a number and spin a wheel, use some of your hole cards and some of the ones on the table. However, the variation of results can be much less simple; the sheer number of possible places to put your money on a craps table is dazzling.

Sample game: Twentybone

Twentybone is a beat-the-bank game played with 20-sided dice, based on the familiar roll for attacks and skill checks.

The house: Twentybone originated in a casino deep in the back alleys of a major city. The casino’s owner favors exciting games with lots of randomness, and his oft- inebriated patrons appreciate that too. Bones are rattled all night long, and cheaters who sneak in loaded dice find that some of their bones get rattled as well.

The equipment: To play, you need some d20s. A whole lot of them. A dealer and a “dice girl” run the game.

The mechanic: On each round, players can buy any number of d20s they want. The standard peasant’s-wage cost for a d20 is a copper piece, though at some tables a player can spend a silver piece, a gold piece, a platinum piece, or even more for a die. When all dice have been purchased, the players all roll their dice. Then the house rolls a die. Every player die that beats the house die gets paid off with two coins for every one coin it was bought for. For the player, a 1 always loses, and a 20 always wins.

The odds: The player has a 47.75 percent chance of winning. 1’s don’t beat anything, 2’s only beat house 1’s, 3’s beat house 1’s and 2’s, and so on. The exception is player 20’s, which have a special advantage of beating house 20’s.

The payout: The player will win 9.55 coins for every 10 coins he bets. The fact that a player is paid two coins on every win obscures the fact that the player gave over a coin to buy the die. Accounting for this, every successful bet’s payout is 1-to-1.

Odds: The odds are the percentage chances that a player will win money. A player’s percentage chance of winning should be somewhat less than 50 percent for the house to make money. In any casino, the house will retain some “edge,” which is the profit the house will make on a long series of bets. So if a player plays a game where he wins 9 silver pieces for every gold piece he gives the house, the house edge is 10 percent.

Payout: The payout is the rate of return a player gets when he wins, usually double the odds. It’s important to understand that for a game of pure chance, all choices must lead to the same payouts over time. Think of the roulette board. A straight-up bet on a single number has a 37-to-1 chance of hitting, and pays 35-to-1. A bet on all of the numbers 1–12 has a 2.167-to-1 chance of hitting, and pays 2-to-1. A bet on red has a 1.111-to-1 chance of hitting, and pays 1-to-1. Doing the math on these bets show that they all have the same rate of return: a player loses 5.3 cents for every dollar bet.