This paper provides a comprehensive Optimality Theoretic formalization of a Finnish language game. In opposition to earlier rule-based studies, the present analysis motivates the sometimes arbitrary-looking patterns of the game and brings together various phenomena under a unified set of universal constraints. The paper also demonstrates the close relationship between language games and natural languages by showing how the patterns of the game are analysable with the help of constraints of ordinary languages, or constraints that deviate only minimally from the original ones. The analysis of the game offers valuable external evidence for the phonology of Finnish with respect to the internal structure of long segments, vowel harmony, syllable markedness and the integrity of diphthongs.