—The paper describes the process of designing a task-oriented continuous speech recognition system for Polish, based on CMU Sphinx4, to be used in the voice interface of a computer game called Rally Navigator. The concept of the game is presented, the stages of creating the acoustic model and the language model are described in details, taking into account the specificity of the Polish language. Results of initial experiments show that as little as 15 minutes of audio material is enough to produce a highly effective single-speaker commandand-control ASR system for the computer game, providing the sentence recognition accuracy of 97.6%. Results of the system adaptation for a new speaker are presented. It is also showed that the statistic trigram-based language model with negative trigrams yields the best recognition results.