This comparative study aimed to investigate the effects of an Augmented-Reality Game-Based Learning application, "StemUp," on the English learning performance and motivation of distinct rural and urban groups of young EFL (English as a Foreign Language) learners. Multiple sources of data collection were employed, including pre- and post-tests, Keller's (1987) ARCS pre- and post-survey, and semi-structured interviews of the fifty participants. Quantitative findings confirmed that the study's AR game-based intervention resulted in a significant improvement in English performance and motivation for both groups, with the students from the rural area improving more in both English performance and motivation compared to those from the urban area. Motivation and enjoyment, gamification, and learning effectiveness were three important qualitative interview themes. Overall, this mixed-methods study found that the learning design employing "StemUp," with its unique 3D AR features/affordances, not only improved participant language gains in vocabulary, speaking, and listening, but also enabled participants to be more engaged and motivated in their English learning. The conclusion is that StemUP is a promising tool for assisting EFL learners in both rural and urban areas in their English language development as well as motivation improvement by facilitating an immersive language learning environment for EFL young learners.