Bitmasks are as old as computing itself and, admittedly, were more useful in the days of memory scarcity and low-level programming. But there’s nothing to stop you using them today, when appropriate.
Factory Method is a creational design pattern that provides an interface for creating objects in a superclass, but allows subclasses to alter the type of objects that will be created.
Flyweight is a structural design pattern that lets you fit more objects into the available amount of RAM by sharing common parts of state between multiple objects instead of keeping all of the data in each object.
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