The basic goal for each level is to get to the end. At the end of each level, you're graded on the following attributes: your speed, your combat, and the amount of coins collected. In levels where you work with your brothers, you'll also be graded on how well you worked together. Succeed in these attributes, and you'll earn turtle coins which can be used to purchase unlockables. If you get an A Rank or higher in a level, you'll also unlock a Challenge Map, which can be played to earn even more turtle coins. Finally, once you've played any level at least once, turtle coins will appear in hard-to-reach spots for you to collect.