Ideas for building a reusable frameworks & systems library

im on my reusable frameworks arc
my current goal is to expand my already existing library to include more systems i can drag and drop into my game

what are some systems that i could make

requirements:

  • must be completely independent from any other systems/frameworks
  • system must not be an entire game, but instead designed to be apart of a game

examples(some stuff i’ve already done):

  • 3d particle system
  • grid managing system
  • cutscene handler
  • UI formatter

other than that im perfectly ok with making any system