Gameobject Component system
This was the first thing I ever made for what would later become Catbox. In our very first TGA2D assignment I made a GameObject and Component class, and have brought them with me in every C++ project since. The system is a replica of how it works in Unity, with the reason being that it would be easy for the other programmers to get into and understand how to use it. I have heard from the other programmers in my group that the programming pipeline is very nice because of this system and the engine as a whole, which is always nice to hear.