We developed and trained a custom AI text classifier to assist Latin language learners in internalising idioms, with a focus on Ciceronian composition. Idioms are mostly language-, sometimes author-specific expressions that cannot be translated directly into another language. The classifier provides interactive feedback on learners' output, effectively gamifying the process of writing in Latin and motivating students to produce more linguistic output. This not only helps learners build confidence, but also acquire a ‘toolbox’ of idioms useful for both output- and input-based activities. We present the results of our experiment conducted across a number of secondary classes in Switzerland. Our tool is freely available at https://latin-ia.hepl.ch/classifier.