ENGLISH·COURSE API
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    CourseSounds: ZodObject<
        { vowels: ZodArray<ZodString>; consonants: ZodArray<ZodString> },
        $strip,
    > = ...

    The sounds a course teaches, as IPA symbols. Vowels include diphthongs and r-coloured vowels; they are kept apart from consonants because a learner reads the two groups differently.