> What if you, one day, want multiple worlds for some reason?
Write code for the application you want, not the set of all applications you might hypothetically want someday. Incur the cost of new features after you decide you want them, not before.
Write code for the application you want, not the set of all applications you might hypothetically want someday. Incur the cost of new features after you decide you want them, not before.
As with any software engineering guideline, there are exceptions. E.g. Java-style loggers are so ubiqitous and "not that mutable", that it's generally good for them to be global.
Edit: also from experience, suddenly wanting two of something where before there was only one, is not that uncommon.