Wagering game having expanding symbol for triggering bonus game

1 . A gaming machine comprising:

a value input device for receiving a wager;

a display region for displaying symbols at respective symbol locations in visual association with at least one active payline, said displayed symbols being selected from a plurality of symbols, said plurality of symbols including an expandable bonus-game symbol; and

wherein in response to said expandable bonus-game symbol being located at a first of said symbol locations, said expandable bonus-game symbol expands to a second of said symbol locations to complete a bonus-game-triggering event along said at least one active payline.

2 . The gaming machine of claim 1 , wherein said display region includes a plurality of reels for said displaying of said symbols, each of said plurality of reels including said expandable bonus-game symbol.

3 . The gaming machine of claim 2 , wherein said plurality of reels are video reels.

4 . The gaming machine of claim 1 , wherein said expandable bonus-game symbol is activated upon a player providing an additional wager input.

5 . The gaming machine of claim 1 , wherein said symbols along said at least one active payline indicate a randomly selected outcome selected from a plurality of outcomes.

6 . The gaming machine of claim 1 , wherein said expandable bonus-game symbol is associated with a multiplier for increasing a bonus payout.

7 . The gaming machine of claim 1 , wherein said expandable bonus-game symbol expands to a third of said symbol locations.

8 . The gaming machine of claim 1 , wherein said expandable bonus-game symbol located at said first of said symbol locations is removed from said first of said symbol locations upon expansion of said expandable bonus-game symbol.

9 . The gaming machine of claim 1 , wherein said bonus-game triggering event includes three of said bonus-game symbol along said at least one active payline.

10 . A method of conducting a wagering game, said wagering game including a plurality of symbols having at least one expandable bonus-game symbol, the method comprising:

receiving a wager input;

displaying a randomly selected outcome for a basic game from a plurality of outcomes that is indicated by a symbol combination from said plurality of symbols;

achieving an outcome including said at least one expandable bonus-game symbol;

expanding said at least one expandable bonus-game symbol to another symbol location to complete a bonus-game triggering symbol combination; and

in response to achieving said bonus-game triggering symbol combination, conducting a bonus game.

11 . The method of claim 10 , further comprising increasing a bonus payout associated with said bonus game via a multiplier associated with said expandable bonus-game symbol.

12 . A computer readable storage medium encoded with instructions for directing a gaming machine to perform the method of claim 10 .

13 . The method of claim 10 , further comprising returning to said basic game after said bonus game is completed.

14 . The method of claim 10 , wherein said displaying further includes displaying a plurality of active paylines, said another symbol location being on one of said active paylines.

15 . The method of claim 10 , further comprising receiving an additional wager input to activate said expandable bonus-game symbol.

16 . A gaming machine for playing a wagering game, comprising:

a display for displaying a plurality of symbols on a plurality of reels, said plurality of symbols indicating a randomly selected outcome selected from a plurality of outcomes in response to receiving a wager input,

an expanding bonus-game symbol feature for expanding at least one of said plurality of symbols on at least one of said plurality of reels; and

a controller coupled to said display, said controller operative to conduct said wagering game and to expand said at least one of said plurality of symbols from a first symbol location to a second symbol location to result in a bonus-game-triggering outcome.

17 . The gaming machine of claim 16 , wherein said controller is operative to expand said at least one of said plurality of symbols upon said gaming machine receiving an additional wager input.

18 . The gaming machine of claim 16 , wherein said display includes a plurality of active paylines, said second symbol location being on at least one of said active paylines.

19 . The gaming machine of claim 18 , wherein at least three symbols along said at least one of said active paylines results in said bonus-game-triggering outcome.

20 . The gaming machine of claim 16 , wherein said controller is operative to receive a selection of at least one of said plurality of reels by a player prior to said expanding of said at least one of said plurality of symbols.