Het ij van uil is based on the renowned children's books about the duo Vos en Haas (Fox and Hare) by Belgian author Sylvia Vanden Heede and Dutch artist Thé Tjong-Khing. This educational game brings the stories to life with professional voice acting and interactive games. There are twelve stories in total, but they are unlocked one by one as the child completes them chronologically and the difficulty is heightened. At certain intervals, while reading, the story is stopped and the children have to solve a relevant puzzle to keep the plot going.
The balancing of the difficulty level is a notable feature. First, the child has to enter his age and reading level (or the lack of one). This information is used to adjust the puzzles and the difficulty of the written sentences. After each game, the player can award a score from one to three according to the difficulty. Using this, the game 'grows' with the child and the content is constantly adjusted based on the ratings and the overall progress.
The title, Het ij van uil, is a wordplay on two confusing sounds in the Dutch language: ei and ij are homophones (pronounced as the English a as in to make). Although both forms are used in many words, the standalone ei means "egg" while ij does not exist. Therefore, the form ij used in the title is not correct, but a common mistake for children at a young age. The literal English translation of the title is: Fox and Hare: The owl's egg.