[copx]

Here:

  Rectangle(100, 100, 400, 400)

That or something very similar [1] draws a rectangle from pixel position (100,100) to (400,400) in many high level 2D graphics environments. Just posting this to point out that you do not have to make things more complicated than necessary.

OpenGL is a standard for hardware accelerated 3D graphics and it is inherently complex because of that. If you just want to do 2D do not bother with it.

[1] http://love2d.org/wiki/love.graphics.rectangle