Sonic Generations (ソニックジェネレーションズ) is a Nintendo 3DS game developed by Sonic Team and published by SEGA. It is a celebration of Sonic the Hedgehog's 20th anniversary, and features both classic and modern Sonic characters. The game has two different gameplay styles - Classic Sonic, which is a 2D side-scrolling platformer, and Modern Sonic, which is a 3D action-adventure. Both styles of gameplay have unique levels and bosses, and the player can switch between them at any time. The game also features a variety of power-ups, such as the ability to transform into Super Sonic, and the ability to use the Homing Attack. The game also features local and online multiplayer modes. Sonic Generations is a fun and exciting game that celebrates the 20th anniversary of Sonic the Hedgehog.