I Spy Castle for Nintendo DS is an adventure-puzzle game designed for younger players, based on the popular I Spy book series. In this game, players explore a medieval castle setting to uncover secrets and solve the king's mission by completing riddles and hidden-object challenges. The game combines elements of exploration and education, tasking players with finding specific items within beautifully illustrated scenes. Its interactive point-and-click gameplay encourages observation skills, critical thinking, and problem-solving abilities, framed in an engaging, themed narrative suitable for children.