2 Games in 1: Sonic Advance + ChuChu Rocket! is a compilation game:

-Sonic Advance: Sonic the Hedgehog has arrived for his first ever adventure on a Nintendo console. Sonic Advance combines elements from the original Sonic series on Sega's Genesis, as well as from the Dreamcast Sonic Adventure series.

Choose from Sonic, Knuckles, Tails, or Amy and take them through level after level of fast gameplay and ring collecting, dodging enemies in your path towards the final showdown with Dr Robotnik (aka Dr Eggman). Collect Chaos Emeralds along the way to transform into Super Sonic for added speed, and train your Chao to exchange them into Sonic Adventure 2 Battle on the Nintendo GameCube. You can also play four-player battle modes with your friends, using one game cart between 4 GBAs.

-ChuChu Rocket!: ChuChu Rocket is an action puzzler, designed predominantly as a multi-player game. You have indirect control over mice, and must guide them to the safety of a rocket, and away from a cat. You do this by placing arrows on the ground, which they will follow. The multi-player game is a frantic all-against-all duel, in which each player's mice will only follow instructions of their own colour. You can play this mode on your own against CPU opponents, or take on a series of predefined puzzles.