Sonic Team was interested in making "Sonic Heroes"s narrative feature characters teaming up to overcome evil, rather than "Sonic Adventure"s approach of individual character stories. This led to the conception of the "team action" concept. Iizuka stated Sonic Team had a considerable amount of freedom in designing the game due to its new scope. The Chao-raising system—a staple of the "Sonic Adventure" games—was removed because Sonic Team feared it would disrupt the pace. To improve replay value, the grading system was made more difficult. The special stages from the 2D games were revived to "refresh players' minds" and change the pace. Player reactions to previous games influenced the design; for example, the team did not include modes like Big's fishing from "Sonic Adventure" and Tails' shooting from "Sonic Adventure 2" after both were criticized.