Definition: Rewrite each original sentence in order to make it easier to understand by non-native speakers of English. You can do so by replacing complex words with simpler synonyms (i.e. paraphrasing), deleting unimportant information (i.e. compression), and/or splitting a long complex sentence into several simpler ones. The final simplified sentences need to be grammatical, fluent, and retain the main ideas of their original counterparts without altering their meanings.
Input: Before Snow White, the Disney studio had been primarily involved in the production of animated short subjects in the Mickey Mouse and Silly Symphonies series.

Before Snow White, Disney had been mainly into making animated short films in the Mickey Mouse and Silly Symphonies series.