Slots game with improving bonus-winning odds

1. A method, comprising,

executing by a server an online slots game, the server is configured to provide access to remote users having user accounts for playing the online slots game over a network connection via mobile devices;

defining a plurality of tiers for playing the online slots game that includes turns, each tier being assigned an odds value for winning a chance to play a bonus game that is different from the online slots game, odds value of each tier being different from the odds value of other tiers from the plurality of tiers;

receiving user input during the online slots game that causes a user interface to be rendered on a display screen of one of the mobile devices to depict a spinning of wheels, wherein the user input includes a bet for playing each turn;

presenting a user interface for playing the bonus game when a player wins the chance to play the bonus game during a turn, the bonus game being a challenge bonus game;

presenting a user interface for selecting a friend of the player to send a friend challenge game to the friend, the play of the friend challenge game by the friend being tracked by the server to provide an additional bonus to the player that selected the friend for the friend challenge game; and

returning the player to the online slots game after completion of said bonus game and said selection of said friend for the friend challenge game, wherein operations of the method are executed by at least a processor of the server.

2. The method as recited in claim 1 , further comprising,

selecting at random a tier from the plurality of tiers at each turn; and

enabling play of each turn with the selected random tier, wherein chances to win the bonus game at each turn are based on the selected tier.

3. The method of claim 2 , wherein defining a plurality of tiers further includes:

assigning an average reward to each tier, wherein an expected payback for winning the bonus game is constant across all tiers.

4. The method as recited in claim 3 , wherein the expected payback is equal to the odds value times the average reward.

5. The method as recited in claim 3 , wherein defining a plurality of tiers further includes:

assigning lower average rewards to tiers with higher odd values for winning the chance to play the bonus game to keep constant across all tiers an expected payback for winning when playing the bonus game.

6. The method as recited in claim 1 , further including:

using a random number generator to determine an outcome of playing each turn.

7. The method as recited in claim 1 , wherein the bonus game is selected from a group consisting of a common bonus game, or a gifting bonus game, or said challenge bonus game, or another slots game.

8. A computer implemented method, comprising,

executing by a server an online slots game, the server is configured to provide access to remote users having user accounts for playing the online slots game over a network connection;

establishing a plurality of tiers for playing the online slots game that includes turns, each tier being assigned an odds value for winning a chance to play a bonus game that is different from the online slots game;

enabling play of each turn, wherein chances to win the bonus game at each turn are based a selected tier;

presenting to a graphical user interface images associated with the bonus game when a player wins the chance to play the bonus game during a turn;

presenting to the graphical user interface options to send challenge bonus game to a friend, wherein play by the friend of the sent challenge game adds to winnings of said bonus game to the player; and

presenting to the graphical user interface graphics associated with the online slots game after completion of the bonus game, wherein operations of the method are executed by at least a processor of the server.

9. The method as recited in claim 8 , wherein a type of the bonus game is selected from a group consisting of a common bonus game, or a gifting bonus game, or a challenge bonus game, wherein the common bonus game is not a slots game, wherein the gifting bonus game is a slots-type game with different slots symbols than the slots game, wherein the challenge bonus game is game that provides a score and an opportunity to a player to challenge another player to play the challenge bonus game.

10. The method as recited in claim 8 , further including:

using a random number generator to determine an outcome from spinning wheels of the slots game, in response to user input.

11. The method as recited in claim 8 , wherein the player wins the chance to play the bonus game when a predefined bonus-winning combination appears on slots wheels of the slots game.

12. The method as recited in claim 8 , wherein the plurality of tiers further includes:

assigning an average reward to each tier, wherein an expected payback for winning the bonus game is constant across all tiers.

13. The method as recited in claim 8 , wherein the odds value of each tier being different from the odds value of other tiers from the plurality of tiers;

receiving user input during the online slots game that causes a spinning of wheels as depicted on a graphical user interface rendered for the online slots game, wherein the user input is associated with a bet for playing each turn; and

selecting at random a tier from the plurality of tiers at each turn.

14. The method as recited in claim 13 , wherein an expected payback is equal to the odds value times an average reward.

15. The method as recited in claim 8 , wherein operations of the method are performed by a computer program when executed by one or more processors, the computer program being embedded in a non-transitory computer-readable storage medium.

16. A non-transitory computer-readable storage medium storing a computer program for executing by a server an online slots game, the server is configured to provide access to remote users having user accounts for playing the online slots game over a network connection, comprising,

program instructions for establishing a plurality of tiers for playing the online slots game that includes turns, each tier being assigned an odds value for winning a chance to play a bonus game that is different from the online slots game;

program instructions for enabling play of each turn, wherein chances to win the bonus game at each turn are based a selected tier;

program instructions for presenting to the graphical user interface images associated with the bonus game when a player wins the chance to play the bonus game during a turn;

program instructions for presenting to the graphical user interface options to send challenge bonus game to a friend, wherein play by the friend of the sent challenge game adds to winnings of said bonus game to the player; and

program instructions for presenting to the graphical user interface graphics associated with the online slots game after completion of the bonus game.

17. The computer readable medium of claim 16 , further including:

program instructions for using a random number generator to determine an outcome from spinning wheels of the slots game, in response to user input.

18. The computer readable medium of claim 16 , wherein the player wins the chance to play the bonus game when a predefined bonus-winning combination appears on slots wheels of the slots game.

19. The computer readable medium of claim 16 , wherein the plurality of tiers further includes:

program instructions for assigning an average reward to each tier, wherein an expected payback for winning the bonus game is constant across all tiers.

20. The computer readable medium of claim 16 , wherein the odds value of each tier being different from the odds value of other tiers from the plurality of tiers;

program instructions for receiving user input during the online slots game that causes a spinning of wheels as depicted on a graphical user interface rendered for the online slots game, wherein the user input is associated with a bet for playing each turn; and

program instructions for selecting at random a tier from the plurality of tiers at each turn.