What do you need to know to create a 2D engine?

Question

C++ / C#

What do you need to create a universal game engine, what skills do you need to have?

Answer 1

C, C++, OpenGL, OpenAL, Bullet/Box2D, glfw, glm, glew, GLSL, vectors, matrices and all linear algebra. Data formats, data structures. Rendering pipeline and video card operation mechanisms. Well, some kind of UI framework.