Educational programming games (EPGs) build computational thinking (CT), a vital 21st-century skill. A core design challenge is how pedagogical and gameplay challenges are integrated to balance educational objectives with player engagement. This study formalizes two contrasting challenge design patterns that reflect distinct integration strategies: extrinsic programming challenges (C1), a pedagogy-oriented design where programming is the core challenge enforced through external constraints; and intrinsic programming challenges (C2), a gameplay-oriented design where programming serves as a tool for overcoming gameplay challenges raised by in-game puzzles. To examine these challenge design patterns, we developed two isomorphic EPGs WannaBone1 (C1) and WannaBone2 (C2), each featuring 20 levels introducing sequences, loops, conditionals, and global variables. A controlled classroom study with 306 primary school students reveals that both designs improve CT, whereas C2 yields significantly higher intrinsic learning motivation and high-order immersion of flow. These findings indicate that a gameplay-oriented rather than pedagogy-oriented design perspective better unites education and entertainment, guiding future EPGs design.