This study is aimed to develop a face-to-face collaborative English vocabulary acquisition game system on portable devices, called Wireless Crossword Fan-Tan Game (WiCFG). One class of 32 primary school students in Taiwan participated in this study. Students' learning outcome, motivation, and attitude were collected and analyzed. In their small group interaction, we analyzed and generalized three interaction modes: "Face-to-face interaction", "Device-media interaction" and "Human-device interaction". Significantly, a "face-to-face portable-device-mediated interaction module" was proposed. The preliminary research findings indicate that adopting the WiCFG could improve the learning outcome of lower-achievement learners. Using the WiCFG had positive enhancements of learning motivation and engagement. In the group observation, using the WiCFG improved learners more interdependent in group collaborative learning and was generally well-received by the English teacher and the students.