You are Good Guy, and you are on a quest to defeat Bad Guy, the only other guy in this area of The World.
You start in the forest. Somewhere within the forest are a pair of flippers, which will allow you to swim in the river. Somewhere along the banks of the river there is a key to the White Castle. Within the White Castle are a protective crown and a deadly weapon (it looks like a red star thingy). These two items are needed to defeat Evil Guy.
Evil Guy lives in the Black Castle, which you can get to through the desert. Conveniantly enough, the key to the Black Castle is somewhere in the desert.
Find Evil Guy in the Black Castle while wearing the crown and weapon and you win! If you lack either the crown or weapon, the screen will flash only red, and you will loose!