We describe two versions of a prototype system for computer assisted language learning hosted on a mobile device. In both versions, the student is given prompts by the machine, which they then have to render in the L2. The two versions differ with respect to the modality of the prompt: one presents it as an L1-based text string, while the other one presents it in pictorial form. The two versions were tested on a group of 32 high school students as part of the Geneva University Student Week. Our findings suggest that male students found the pictorial version significantly easier to use, while female students preferred the text version.