Your objective in King's Rush is to obliterate everything on you path. Destroy fortresses, scary creatures and earn some good money by doing it. The coins you collect in the field can be used to upgrade your battering ram in a variety of ways, increasing stats like ramming speed, armor and reload times.
You use dynamite to blast your royal ram downhill, using [SPACEBAR] to jump and [X] to fire cannonballs at obstacles and enemies. Each little impact saps some tiny amount of health, so keep your wits about you.