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Until the 1990s, players dropped coins into slots to activate them for each spin. That changed in live casinos when bill validators and credit meters were added to machines, allowing bettors to play off credits instead of cash. Online slots are similar in that players advance their accounts with each spin by either depositing real money or reloading funds.
While the fundamentals of probability are at play in slot machines, designers have added many other features to appeal to gamblers. Video monitors and 3D graphics are bringing some of the visual appeal of computer games to land-based casino floors, while themes based on pop culture are attracting new generations of gamblers.
A slot’s volatility is an important factor in determining how often it pays out and the amount of winnings it generates. A machine with low variance offers frequent wins and small amounts of winnings, while a high-volatility game has rare wins but larger amounts of winnings. Several methods can be used to determine a slot’s volatility, including playing for free in a demo mode and tracking the results of past plays. The developer of a slot can also provide information on the game’s volatility in its documentation.