Electronic gaming system and method of providing a feature game with bonus levels

1. A method of conducting a wagering game, said method comprising:

conducting a base game on a plurality of base game reels of an electronic gaming machine;

detecting a trigger condition in the base game;

replacing two or more base game reels of the plurality of base game reels with two or more feature game reels;

initiating a feature game on the two or more feature game reels in response to detecting the trigger condition, the feature game including a plurality of feature game rounds;

conducting a feature game round of the plurality of feature game rounds;

detecting a bonus level trigger condition in the feature game;

unlocking a bonus level of a plurality of bonus levels based on the bonus level trigger condition, the bonus level including a bonus award;

applying the bonus award to a subsequent feature game round of the plurality of feature game rounds; and

determining an outcome of the subsequent feature game round.

2. A method as claimed in claim 1 , wherein the feature game comprises setting an initial number of feature game reels to replace a same number of base reels based on the trigger condition.

3. A method as claimed in claim 1 , wherein the trigger condition comprises a game round outcome that includes a plurality of aligned scatter symbols.

4. A method as claimed in claim 3 further comprising setting an initial number of feature game reels to replace a same number of base reels based on a number of the plurality of aligned scatter symbols.

5. A method as claimed in claim 1 , wherein the two or more feature game reels include stacked diamond symbols and credit prizes.

6. A method as claimed in claim 1 further comprising setting an initial number of the feature game rounds according to whether or not an ante bet is made.

7. A method as claimed in claim 1 further comprising determining a number of the plurality of bonus levels based on an outcome of one or more feature game rounds.

8. A method as claimed in claim 7 further comprising successively modifying the number of the plurality of bonus levels based on successive outcomes of the plurality of feature game rounds.

9. A method as claimed in claim 7 , further comprising setting the number of the plurality of bonus levels according to a number of identical symbols displayed on the two or more feature game reels.

10. A method as claimed in claim 1 , wherein at least one of the plurality of bonus levels comprises multiplication of a win by an integer or other value greater than one.

11. A method as claimed in claim 1 , wherein at least one of the plurality of bonus levels comprises an award of a number of extra feature game rounds or an award of a number of extra feature game rounds determined according to the bonus level trigger condition.

12. A method as claimed in claim 1 , wherein at least one of the plurality of bonus levels comprises an additional winning combination of reel symbols.

13. A method as claimed in claim 1 , wherein at least one of the plurality of bonus levels comprises an additional scatter symbol or wildcard.

14. A method as claimed in claim 1 , wherein the bonus level trigger condition comprises a feature game round outcome in which the two or more feature game reels display at least a predefined minimum number of identical symbols.

15. A method as claimed in claim 1 , wherein the bonus level trigger condition comprises a feature game round outcome in which the two or more feature game reels display only identical symbols.

16. A method as claimed in claim 15 , further comprising setting a number of the plurality of bonus levels according to a number of the two or more feature game reels that display only the identical symbols.

17. A method as claimed in claim 1 , wherein at least one of the plurality of bonus levels and an initial number of feature game rounds are based on whether or not an ante bet was made.

18. A game controller for a gaming system, the game controller configured to:

conduct a base game on a plurality of base game reels;

detect a trigger condition in the base game;

replace two or more base game reels of the plurality of base game reels with two or more feature game reels;

initiate a feature game on the two or more feature game reels in response to the trigger condition, the feature game including a plurality of feature game rounds;

conduct a feature game round of the plurality of feature game rounds;

detect a bonus level trigger condition in the feature game;

unlock a bonus level of a plurality of bonus levels based on the bonus level trigger condition, the bonus level including a bonus award;

apply the bonus award to a subsequent feature game round of the plurality of feature game rounds; and

determine an outcome of the subsequent feature game round.

19. A method as claimed in claim 1 further comprising:

determining that an initial number of feature game rounds are completed; and

determining an outcome of the feature game.

20. A gaming system comprising:

a player interface comprising a display for displaying game outcomes to a player; and

a game controller configured to:

conduct a base game on a plurality of base game reels;

detect a trigger condition in the base game;

replace two or more base game reels of the plurality of base game reels with two or more feature game reels;

initiate a feature game on the two or more feature game reels in response to detecting the trigger condition, the feature game including a plurality of feature game rounds;

conduct a feature game round of the plurality of feature game rounds;

detect a bonus level trigger condition in the feature game;

unlock a bonus level of a plurality of bonus levels based on the bonus level trigger condition, wherein the bonus level including a bonus award;

apply the bonus award to a subsequent feature game round of the plurality of feature game rounds; and

determine an outcome of the subsequent feature game round.