during play of the base game or the bonus event advancing to the next bonus level may also result in the player being provided with additional credits 102 fig1 a the player has no idea which tool 110 will be effective for advancing into each bonus level 705 706 in a preferred embodiment a random number generator function 708 determines which tool or tools 110 will be effective for advancing the player at the time of play of the bonus event fig7 shows examples of tools 110 fig1 a that may be randomly selected for entry into each level 704 705 706 of the bonus event winning tools 110 are selected from a pool of five different tools 110 herein exemplified as tnt 710 spade 712 pick 714 laser 716 and phaser 718 shown schematically as simplified shapes the symbols for these tools 110 are shown on each level for advancing into the next level as depicted any three of the five tools 710 712 714 716 718 may be randomly selected by a random number generator 200 fig1 one of these three tools is subsequently required for advancement 722 beyond each of the first bonus level 704 and subsequent.