During one of my university courses, we were tasked with building code snippets used in computer graphics. These snippets went from camera perspective computation to scene setup and game-like logic. After the courses was complete I kept working on these snippets and assembled them into a full engine. I ended up scrapping the project as the nature of the way I build the engine made it difficult to work on in the long run and I spent much more time on fixing weird edge cases rather than doing what I was actually interested in. Before archiving the project the engine supported the following feature: Blinn-Phong and PBR rendering, Shadow Mapping, Different methods for collision detection, World Space 3D Text and some basic particle generation.
I ultimately scrapped the project and moved on to different ones, one of these involved also exploring Vulkan which offered more promise as a modern graphics library.