The Cart Challenge is the second Challenge Act of Planet Wisp Act 2 in the console/PC version of Sonic Generations. It is unlocked after clearing every Stage in the modern era and is playable only as Modern Sonic.
The Cart Challenge is a modified version of the semi-final section of Planet Wisp Act 2, which revolves around boosting on top of Carts to reach the rocket tower. The entire Act takes place in a 2.5D perspective. The path to the tower recommends usage of Carts which always lead to the higher sections of the Act. While there exist solid floors below the Cart tracks, which work as safety nets for the player in case they should miss or fall off a Carts and needs to go back up, they are usually filled with spikes, rotating spiked balls and flamethrowers (especially during the final sections). In return, the Act offers Time Bonuses.
Some Carts have Egg Pawns riding on them. In such cases, the player can either destroy the Egg Pawn, or sit just behind them. This Act also make practical use of the Cases which the player must activate/deactivate with switches to make/dissolve platforms to proceed. However, some switches last only a short time.
Sonic starts the Challenge Act facing a monorail track for Carts. When on a Cart, accelerate by holding down /. During rides with Carts, the player can take small shortcuts to Carts ahead using the Dash Rings that sometimes appear above the Cart tracks. Once the player reaches the end of the first section, they should encounter a series of deactivated Cases that they must activate to scale them. Alternatively, the player can use a Spring that can be reached by jumping just before the end of the section's Cart track.
The second Cart-riding section is short and the Carts are without Egg Pawns. At the end of this section, a series of platforms will fall down. Use them to go up, and the player should activate another switch for a Case to go to the final section. The final Cart-riding section is similar to the first one, except it is filled with more traps and has two Cart tracks above the first one that lead to the Goal Ring.