Online slot games use various techniques to allow players a chance of winning additional credits without having to place any wagers. The most common methods are through the free spins the bonus round and the bonus game on the second screen. In the free spins bonus round players are allowed to spin the reels a number of times without having to place wagers but are entitled to the payouts. In the bonus came on the second screen the players are also able to win bonus credits without staking anything. Recently another method has been increasingly used in certain slot games that is called Tumbling Reels.

Tumbling Reels is a trademark of WagerWorks and this feature is present in a number of their online slot games such as Crystal Caverns and Dynamite Digger. When a payline has a winning combination the player is credited with the amount due for that combination. Then the Tumbling Reels feature comes in to affect. The symbols that make the winning combination disappear from the reels leaving blanks. The symbols immediately above the blanks fall down to fill the void. Then the symbols about those fall down to fill the new voids. Ultimately fresh symbols appear in the relevant reels of the topmost row. Once all the symbols are in place the winning combinations are again assessed and payouts made. The process keeps on repeating any number of times till there are no winning combinations. No wager is deducted for the subsequent payouts. Hence based on the initial wager the player is able to receive a number of payouts on the same spin provided he is lucky.

Apart from creating an opportunity for additional payouts, Tumbling Reels are also aesthetically pleasing. To see the symbols tumbledown and create new combinations a number of times adds to the pleasure of playing these online slot games. There is also an excitement created by the suspense of waiting for new winning combinations to form.

Cryptologic also offers a similar feature in its Casual Game Slots, though not under the name of Tumbling Reels. Its popular online slot Bejeweled is a prime example. Bejeweled scores over the slot games of WagerWorks because of two reasons. It allows vertical paylines in a 5 x 5 matrix and combinations need not be left aligned in the paylines. This results in greater winning combinations and more frequent dropping of symbols. When vertical paylines are replaced by the dropping symbols the visual effect is more fascinating. Another advantage that Bejeweled offers is that its symbols consist of brightly colored precious stones cut into different shapes. This also creates a more pleasing visual affect.

In its Casual Game Slots Cryptologic has changed the structure of some of the games from reels to other formats. One game is Jenga in which the paylines are rows of a tower and symbols are matching blocks. When matching blocks occur in paylines they are removed and other blocks from the top take their place as in Tumbling Reels. Sometimes so many blocks are removed that the tower becomes unstable and tumbles down in a riot of colors.