Dewy's Adventure starts off with a woman telling a story to a young boy under an old and dying tree. Her story is about the Tree of Seven Colors and how a long time ago, it was attacked by the Black Rain. During that time of crisis, the tree created a small hero named Dewy to fight off the Black Rain. He succeeded and the inhabitants of the tree, called Eau, lived in peace for a long time. Then, one day, the Black Rain returned and captured six of the seven color fruits. With its last bit of power, The Tree of Seven Colors once again called for Dewy, and now you have to help him get back the missing fruit and save the kidnapped Eau.
Dewy is a water drop that can change into two other states, ice and vapor. With these simple powers, Dewy will release trapped Eau by sliding into them and take on enemies with his various types of attacks. In his water form, Dewy can jump and slam on top of Black Rain grunts, while in the ice state, he can spin around and knock them out. In the vapor state, Dewy can't move, but he can send down lightning bolts to either destroy or stun his enemies.
The game has a simple design and basic principal that makes it really easy to get into, and also really hard to master. Since you don't physically run Dewy around the screen (he slides around, but more on that later), you have to be really good with your timing and have some quick reflexes so that you can switch between the various states on a moment's notice in order to be the most effective Eau Savior you can be.
If the Story Mode was all Dewy's Adventure had going for it, it would already be a pretty solid product, but to help appeal to a slightly wider audience, namely tweakers, this game also offers an Edit Mode. That's right, you can create your own levels full of enemies and puzzles to not only play by yourself, but also share with your friends over the internet. As you progress in the game, more types of locations, landscape pieces and enemies become unlocked so that you can make bigger and more intricate levels to play and share.