도전 사자성어 Chinese Four-Idiom offers a chance to delve into popular Hanja content at a temporarily discounted price. Originally priced at $1.99, now available at $0.99, this app is tailored for iPod Touch and iPhone users preparing for the Chinese Character Proficiency Test through learning Four-character idioms. By engaging in problem-solving activities, users can effortlessly enhance their understanding of Chinese idioms and characters, progressing from casual learning to mastery.

The program comprises two main sections: [Study of Four-character idioms] and [Completion of Four-character idioms], each containing 900 problems divided into 50 questions per grade level. Users can access instant scoring feedback during problem-solving, review correct answers promptly, and challenge themselves with a random set of 50 questions in [Challenge! Practice]. Additionally, the app allows users to track their progress in [Study History], storing and retrieving results from up to 100 practice tests, and explore the contents through the Four-character idioms list in [Appendix].