Filipino learners' lack of English language proficiency is a major barrier to higher education opportunities and participation in high-value industries. Computer-based learning systems have the potential to increase educational quality, equity, and efficacy in the Global South. However, a key challenge is to design systems that are developmentally and socio-culturally appropriate and engaging for the target learners. In this paper, we describe the design, development, and preliminary testing of "Ibigkas!," a collaborative, mobile phone-based game designed to provide phonemic awareness and vocabulary building support to Filipino learners aged 10-12.