referring to the drawings , there is shown a gaming system having a game controller arranged to implement a game where a player is allocated a number of game rounds to achieve a target outcome . during the game rounds contributions towards the outcome are accumulated and the player receives an award if the target outcome is achieved . in an embodiment , the player selects the target outcome from target outcomes having different levels of difficulty with greater awards associated with higher difficulty , thus introducing a tension between the player &# 39 ; s selection and the prospects of success . the gaming system can take a number of different forms . in a first form , a stand alone gaming machine is provided wherein all or most components required for implementing the game are present in a player operable gaming machine . in a second form , a distributed architecture is provided wherein some of the components required for implementing the game are present in a player operable gaming machine and some of the components required for implementing the game are located remotely relative to the gaming machine . for example , a “ thick client ” architecture may be used wherein part of the game is executed on a player operable gaming machine and part of the game is executed remotely , such as by a gaming server ; or a “ thin client ” architecture may be used wherein most of the game is executed remotely such as by a gaming server and a player operable gaming machine is used only to display audible and / or visible gaming information to the player and receive gaming inputs from the player . however , it will be understood that other arrangements are envisaged . for example , an architecture may be provided wherein a gaming machine is networked to a gaming server and the respective functions of the gaming machine and the gaming server are selectively modifiable . for example , the gaming system may operate in stand alone gaming machine mode , “ thick client ” mode or “ thin client ” mode depending on the game being played , operating conditions , and so on . other variations will be apparent to persons skilled in the art . irrespective of the form , the gaming system comprises several core components . at the broadest level , the core components are a player interface 50 and a game controller 60 as illustrated in fig1 . the player interface is arranged to enable manual interaction between a player and the gaming system and for this purpose includes the input / output components required for the player to enter instructions and play the game . components of the player interface may vary from embodiment to embodiment but will typically include a credit mechanism 52 to enable a player to input credits and receive payouts , one or more displays 54 , a game play mechanism 56 comprising one or more input devices that enable a player to input game play instructions ( e . g . to place bets ), and one or more speakers 58 . the game controller 60 is in data communication with the player interface and typically includes a processor 62 that processes the game play instructions in accordance with game play rules and outputs game play outcomes to the display . typically , the game play instructions are stored as program code in a memory 64 but can also be hardwired . herein the term “ processor ” is used to refer generically to any device that can process game play instructions in accordance with game play rules and may include : a microprocessor , microcontroller , programmable logic device or other computational device , a general purpose computer ( e . g . a pc ) or a server . a gaming system in the form of a stand alone gaming machine 10 is illustrated in fig2 . the gaming machine 10 includes a console 12 having a display 14 on which are displayed representations of a game 16 that can be played by a player . a mid - trim 20 of the gaming machine 10 houses a bank of buttons 22 for enabling a player to interact with the gaming machine , in particular during game play . the mid - trim 20 also houses a credit input mechanism 24 which in this example includes a coin input chute 24 a and a bill collector 24 b . other credit input mechanisms may also be employed , for example , a card reader for reading a smart card , debit card or credit card . a player marketing module ( not shown ) having a reading device may also be provided for the purpose of reading a player tracking device , for example as part of a loyalty program . the player tracking device may be in the form of a card , flash drive or any other portable storage medium capable of being read by the reading device . a top box 26 may carry artwork 28 , including for example pay tables and details of bonus awards and other information or images relating to the game . further artwork and / or information may be provided on a front panel 29 of the console 12 . a coin tray 30 is mounted beneath the front panel 29 for dispensing cash payouts from the gaming machine 10 . the display 14 shown in fig2 is in the form of a video display unit , particularly a cathode ray tube screen device . alternatively , the display 14 may be a liquid crystal display , plasma screen , any other suitable video display unit , or the visible portion of an electromechanical device . the top box 26 may also include a display , for example a video display unit , which may be of the same type as the display 14 , or of a different type . fig3 shows a block diagram of operative components of a typical gaming machine which may be the same as or different to the gaming machine of fig2 . the gaming machine 100 includes a game controller 101 having a processor 102 . instructions and data to control operation of the processor 102 are stored in a memory 103 , which is in data communication with the processor 102 . typically , the gaming machine 100 will include both volatile and non - volatile memory and more than one of each type of memory , with such memories being collectively represented by the memory 103 . the gaming machine has hardware meters 104 for purposes including ensuring regulatory compliance and monitoring player credit , an input / output ( i / o ) interface 105 for communicating with peripheral devices of the gaming machine 100 . the input / output interface 105 and / or the peripheral devices may be intelligent devices with their own memory for storing associated instructions and data for use with the input / output interface or the peripheral devices . a random number generator module 113 generates random numbers for use by the processor 102 . persons skilled in the art will appreciate that the reference to random numbers includes pseudo - random numbers . in the example shown in fig3 , a player interface 120 includes peripheral devices that communicate with the game controller 101 and comprise one or more displays 106 , a touch screen and / or buttons 107 , a card and / or ticket reader 108 , a printer 109 , a bill acceptor and / or coin input mechanism 110 and a coin output mechanism 111 . additional hardware may be included as part of the gaming machine 100 , or hardware may be omitted as required for the specific implementation . for example , while buttons or touch screens are typically used in gaming machines to allow a player to place a wager and initiate a play of a game any input device that enables the player to input game play instructions may be used . in addition , the gaming machine 100 may include a communications interface , for example a network card 112 . the network card may , for example , send status information , accounting information or other information to a central controller , server or database and receive data or commands from the central controller , server or database . fig4 shows a block diagram of the main components of an exemplary memory 103 . the memory 103 includes ram 103 a , eprom 103 b and a mass storage device 103 c . the ram 103 a typically temporarily holds program files for execution by the processor 102 and related data . the eprom 103 b may be a boot rom device and / or may contain some system or game related code . the mass storage device 103 c is typically used to store game programs , the integrity of which may be verified and / or authenticated by the processor 102 using protected code from the eprom 103 b or elsewhere . it is also possible for the operative components of the gaming machine 100 to be distributed , for example input / output devices 106 , 107 , 108 , 109 , 110 , 111 to be provided remotely from the game controller 101 . fig5 shows a gaming system 200 in accordance with an alternative embodiment . the gaming system 200 includes a network 201 , which for example may be an ethernet network . gaming machines 202 , shown arranged in three banks 203 of two gaming machines 202 in fig5 , are connected to the network 201 . the gaming machines 202 provide a player operable interface and may be the same as the gaming machines 10 , 100 shown in fig2 and 3 , or may have simplified functionality depending on the requirements for implementing game play . while banks 203 of two gaming machines are illustrated in fig5 , banks of one , three or more gaming machines are also envisaged . one or more displays 204 may also be connected to the network 201 . for example , the displays 204 may be associated with one or more banks 203 of gaming machines . the displays 204 may be used to display representations associated with game play on the gaming machines 202 , and / or used to display other representations , for example promotional or informational material . in a thick client embodiment , game server 205 implements part of the game played by a player using a gaming machine 202 and the gaming machine 202 implements part of the game . with this embodiment , as both the game server and the gaming device implement part of the game , they collectively provide a game controller . a database management server 206 may manage storage of game programs and associated data for downloading or access by the gaming devices 202 in a database 206 a . typically , if the gaming system enables players to participate in a jackpot game , a jackpot server 207 will be provided to perform accounting functions for the jackpot game . a loyalty program server 212 may also be provided . in a thin client embodiment , game server 205 implements most or all of the game played by a player using a gaming machine 202 and the gaming machine 202 essentially provides only the player interface . with this embodiment , the game server 205 provides the game controller . the gaming machine will receive player instructions , pass these to the game server which will process them and return game play outcomes to the gaming machine for display . in a thin client embodiment , the gaming machines could be computer terminals , e . g . pcs running software that provides a player interface operable using standard computer input and output components . servers are also typically provided to assist in the administration of the gaming network 200 , including for example a gaming floor management server 208 , and a licensing server 209 to monitor the use of licenses relating to particular games . an administrator terminal 210 is provided to allow an administrator to run the network 201 and the devices connected to the network . the gaming system 200 may communicate with other gaming systems , other local networks , for example a corporate network , and / or a wide area network such as the internet , for example through a firewall 211 . persons skilled in the art will appreciate that in accordance with known techniques , functionality at the server side of the network may be distributed over a plurality of different computers . for example , elements may be run as a single “ engine ” on one server or a separate server may be provided . for example , the game server 205 could run a random number generator engine . alternatively , a separate random number generator server could be provided . further , persons skilled in the art will appreciate that a plurality of game servers could be provided to run different games or a single game server may run a plurality of different games as required by the terminals . in the embodiment , the game is triggered by trigger monitor 626 a as a feature game from a base game conducted by base game controller 626 and displayed in a first display area 54 a . in the embodiment , the feature is conducted as a second screen feature and is displayed in a second display area 54 b which may be on a separate display to the first display area 54 a . the feature can be triggered in accordance with any of the know eligibility criteria including based on turnover , by being purchased in the base game , by a system event or by a symbol combination in the base game . the selection processor 623 is arranged to offer via display 54 a plurality of different selectable target outcomes specified by target outcome data 642 . in the embodiment , the player operates game play mechanism 56 to select one of the target outcomes . in an alternative embodiment , the player may be allowed to construct the target outcome from a plurality of components specified by target outcome data 642 . for example , the player may be offered a plurality of different start components to the target outcome and , depending on the selected start , a plurality of different end components . in such embodiments , an award may be made for achieving a component of the target outcome . in some embodiments , the selection processor may make a default selection based on game rules if a time out condition is met . the game round controller 622 a of outcome generator 622 then conducts a series of game rounds for achieving the target outcome ; the initial number of game rounds being related to the selected target outcome . each game round involves a symbol selector 622 b selecting symbols specified by symbol data 641 . the selected symbols are advised to the display controller 625 which causes them to be displayed on display 54 at a set of display positions . one example of selecting symbols is for the symbol selector 622 b to access the random number generator 621 to select symbols using the game rules 644 for display as a plurality of spinning reels . the symbol sets 641 can specify a sequence of symbols for each reel such that the symbol selector 622 b can select a symbol by selecting a stopping position in the sequence . the selected symbols are then evaluated by symbol evaluator 622 c to determine whether they include any contributions towards the target outcome , for example , a specific symbol combination that contributes toward the target outcome . accumulator 622 d accumulates any contribution and progress towards the target outcome is displayed on display 54 b by display controller 625 . in some embodiments , players may be entitled to purchase additional contributions . the game round controller 622 a continues to conduct game rounds until all the game rounds have been exhausted . the number of available game rounds 644 is specified by the game rule data 644 and the number of game rounds may be used as one factor to control the difficulty of achieving the target outcome . in some embodiments , particular outcomes of symbol selection may cause the number of game rounds to be varied , for example by adding to or subtracting from the current number of game rounds . the remaining number of game rounds is stored as the game round data 643 . the player may also be able to place an additional bet to buy more game rounds . accordingly , it will be appreciated that the game round controller 622 a is arranged to continue to conduct rounds until either the accumulator 622 d accumulates sufficient contributions to achieve the target outcome or the game rounds are exhausted . if sufficient contributions are made , the award determiner 624 is advised and the award determiner 624 determines the prize 645 corresponding to the target outcome 642 , updates the credit meter 646 and controls the display by means of display controller 625 to show the awarding of the prize . it will be appreciated that contributions towards the outcome can be achieved in a number of ways , for example , they can relate to a specific symbol combination created by selecting a set of symbols for display , they can be created by specific symbol being in the set of symbols , etc . a person skilled in the art will appreciate that other techniques could be used to select symbols including drawing a card from a set of cards , rolling a dice , etc . by way of example , the contributions can be in the form of a movement towards an outcome in the form of a destination or by removing an obstacle to reaching a destination . in such embodiments , the relative difficulty of achieving an outcome can be controlled in a number of ways , including the amount of movement needed to reach an destination associated with the target outcome ( which may be an origin ), the number of obstacles , or the number of game rounds . accordingly , as the difficulty of achieving an outcome can be controlled , there is a tension between a player &# 39 ; s selection of a target outcome and the player &# 39 ; s prospects of achieving the outcome . persons skilled in the art will appreciate that the target outcome may be chosen in some other manner than by a player . for example , the target outcome be defined based on a player &# 39 ; s previous expenditure in the game , the number times they have entered the feature game or the manner in which they enter the feature game , for example a particular combination achieved when entering the feature game . the method is summarised in fig7 which shows a feature being triggered 705 , a player selection of a target outcome being made 710 , and a set of bonus games started 715 . in each bonus game round , symbols are selected 720 and it is determined 725 whether this results in a contribution to the outcome . if it does , the contribution is accumulated 730 and is determined 735 whether the outcome has been achieved . if the outcome has been achieved , an award is made 740 . if not , the number of allocated game rounds is decremented 745 and is determined whether the allocation of game rounds has been exhausted 750 in which case the game ends 755 . if the allocation has not been exhausted , the method proceeds by selecting the symbols for a further game round 720 . fig8 shows an exemplary display 800 of an example where a player is given a limited number of total feature spins and the player can select three levels of difficulty and hence select from three outcomes . the higher the number of obstacles , the greater the reward at the end , as denoted by the increasing sizes of the treasure chests 850 , 840 , 830 . in this example , the theme is of salvaging treasure from a wreck 823 and accordingly a salvage ship 822 is displayed and a diver 821 indicates the player &# 39 ; s current progress towards the target outcome . the target outcomes are each of the three treasure chests 830 , 840 and 850 . there are obstacles 831 , 832 , 841 , 842 and 851 between the player position 821 and the target outcomes 830 , 840 and 850 . the player has a trade off for the higher prize of less chance to actually getting the prize . the obstacles are chosen to fit with the theme and are displayed as blocked doors , rubble , barrels , hanging nets , etc . reels are displayed in areas 811 , 812 and 813 , where the player has a chance to spin up items that help clear the obstacles . for example , the player may spin up a key to open a lock door . once the player reaches a treasure chest 830 , 840 or 850 the remaining spins are used to drag the treasure chest back to the salvage ship . thus , the higher level of obstacles and the more positions the player is required to traverse to get the obstacle back to the ship 822 depict the level of difficulty . it will be appreciated that the individual reel spins of each game outcome displayed in the reels 811 to 813 contribute to towards the players progress to achieving the target outcome and that this accumulation of contributions is represented by the diver &# 39 ; s current position and status ( e . g . the direction the diver is shown travelling in , whether or nor they are carrying the treasure , etc ). a person skilled in the art will appreciate that there can be a number of variations to this example , for example , it may be possible for obstacles to be put back after they have been removed or for additional obstacles added in response to a particular outcome of the reels 811 or 813 or for game rounds ( i . e . spins ) to be added or subtracted . in the above example , the target outcome combines the player &# 39 ; s trip from an origin to a destination and back to the origin . in other embodiments the player may journey solely to the destination . obstacle replacement could be dependent on the outcome of reels , duration of time or the amount of funds bet . in one embodiment , the player could purchase the removal of an obstacle . persons skilled in the art will also appreciate that the method of the embodiment could be embodied in program code . the program code could be supplied in a number of ways , for example on a computer readable medium , such as a disc or a memory ( for example , that could replace part of memory 103 ) or as a data signal ( for example , by transmitting it from a server ). it will be understood to persons skilled in the art of the invention that many modifications may be made without departing from the spirit and scope of the invention . it is to be understood that , if any prior art publication is referred to herein , such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art , in australia or any other country . in the claims which follow and in the preceding description of the invention , except where the context requires otherwise due to express language or necessary implication , the word “ comprise ” or variations such as “ comprises ” or “ comprising ” is used in an inclusive sense , i . e . to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention