Mine is quite minimalistic, and relies for the D runtime and standard library (or other D libraries) for many things. Also my engine is primarily geared towards retro pixelart games, and works as such. Currently, the CPU renders to a low-res texture (as seen in emulators), which is then stretched to a higher resolution, later on it'll replaced by custom shaders that do color lookup and render directly to a texture (which is quite complicated, simpler methods would cause easily misalignable pixels, thus defeating the engine's purpose, even if some likes the "smooth" scaling from other engines).