Challenge Mode in Pikmin 2 is very different from the one in the first game. To unlock Challenge Mode, you need to get The Key from the final floor of the Citadel of Spiders in the Perplexing Pool. Challenge Mode takes palce in many cave areas and you'll need to collect The Key to advance to the next level or exit the level. In each level, you are timed to advance to the next level. You can get a White Flower, which means you completed it but some Pikmin died or a Pink Flower, which means you beat the level with all of your Pikmin intact. There are 30 levels in all.

Levels