I've started using your engine a little while ago. I've encountered a problem when I start moving the camera.
I have the camera looking straight down the z-axis, with objects arranged in x-y space. When I move it along the x-y plane, I notice that objects with a z-value that is not 0 tend to "drift" in relation to each other, much like a perspective camera would minus the scaling.
I'm guessing this the parallax scrolling feature in your engine? How would I turn this off?