in the game are divided into "zones", each consisting of two acts of normal gameplay then a 3D boss battle. The course of the game differs depending on whether Sonic or Blaze is chosen; the seven zones are the same, but are accessed in different orders. During boss battles, Blaze fights Doctor Eggman and Sonic fights an Eggman doppelgänger called Eggman Nega. As the characters' stories progress, they meet each other several times and unite in the final zone that comes after the seventh. The game features special stages the player can access via certain handles in order to obtain the Chaos Emeralds. These Special Stages resemble those of Sonic the Hedgehog 2 and use the DS' stylus controls. New features include a grading system that grades the player based on the time it takes for them to complete the level; they can return to levels later to try for a higher grade. There is a point system based on the one in Sonic Advance 2 but displaying points in multiple categories. Sonic Rush introduces a "Tension Gauge" on the left side of the screen which is filled by doing tricks and defeating enemies. The energy it generates allows the player to use boosts of speed while moving; defeating enemies, moving through the level more quickly which results in more points and a higher grade, and when playing as Sonic, accessing the special stage. Although the game is primarily two-dimensional, there are three-dimensional elements which create a 2.5D effect. For the first time in the series, Sonic and Blaze's sprites are rendered in 3D. The game has a two-player mode in which Sonic and Blaze race to the end of a chosen level from the game. There is also a feature in which players who own the game can send a demo of the game to other Nintendo DS users. Plot Blaze the Cat is somehow pulled from her native dimension into Sonic's world. Her world had seven Sol Emeralds—similar to the Chaos Emeralds—but they were stolen by Doctor Eggman. She then makes it her goal to retrieve them. While searching, she meets Cream the Rabbit and is surprised by her politeness. Meanwhile, Sonic is searching for the Chaos Emeralds, which have been stolen by Doctor Eggman Nega, Eggman's alternate counterpart from Blaze's dimension. Sonic briefly encounters Blaze during his search, but she departs before he can question her. His