Adding Files

This might be a dumb question, but how does one add new swift files to a playground / project?

Every featured challenge/playbook/whatever is comprised, of course, of multiple swift files, but I can't seem to find any way to add any files to the blank template outside of the intial "Contents.swift". At the moment I'm looking to use the app standalone, without involving xcode at all.

Adding Files
 
 
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