We describe a web-enabled serious game intended to help German-speaking beginner students of English improve their generative and auditory competence. The tool is built on top of the existing CALL-SLT platform, the architecture of which is briefly described. It offers a short course of 8 interactive lessons using a combined vocabulary of about 450 words, and was developed in collaboration with a secondary school teacher, with the content taken from a commonly used textbook. Lessons are structured as a short dialogue between the student and the machine, where the student is encouraged to use simple language in practical contexts like booking a hotel room, buying clothes, or ordering a meal in a restaurant. A lesson connects together groups of component examples. At each turn, the system starts by playing a short video file in English, and simultaneously displays a piece of text in German indicating to the student how they should reply. The students give a spoken response in English; if they are uncertain how to respond, they can first ask for a help example. After the student answers, the system performs speech recognition, machine translation and matching, and either accepts or rejects. There are multiple paths through the dialogue, controlled by a lesson structure defined in an XML file supplied by the course designer. The overall system is gamified to increase student motivation, using common game elements such as badges. We conclude with a brief description of an informal pre-study carried out on several children aged between 9 and 13. The older children liked the system and found it easy to use, while the younger ones struggled.