When Crash arrives at the arena in his Atlasphere, Rok-Ko gives Crunch a hot rock donned sphere. The notion of simply attacking Crunch by bumping into him will not work and will only drain Crash of health as he takes damage when Crunch touches him, either purpose or accident. The reason why the two marsupials are in spheres is that there are rocks that move about and always bump into each other unless one of the Bandicoots hits a rock. The purpose of the two rocks that are colliding into each other in the arena (and the same purpose applies to the other two phases) is that when all of them are turned blue, a torrent of rocks will hit the Crunch and take health away. So, Crash must turn all of the rocks blue by colliding into them and therefore, allowing a downpour of rocks to hit Crunch.