Proper name for Inverted Cartesian coordinate system? In most 2D computer graphic rendering applications (HTML Canvas, Flash, etc...), the coordinate system used is like this:

My question is, what is the mathematical/technical name for this kind of coordinate system? Inverted Cartesian?
 A: You've tapped into a major incompatability between the standard Math convention taught in Math class, and some CS graphics programming systems (but not all).
I use the term "upside-down y-coordinates" to highlight the problem from a math educator's perspective.
The depth of the problem increases as one delves into more complex spatial problem-solving where vector geometry is advantageous.  Here, you want to have strong conventions for representing spatial directions.  Standard direction-angles increase CCW, but the designers of "upside-down y-coordinate" graphics toolboxes face a dilemma where they are nudged toward having their direction angles increase CW (so that the trig. functions don't need to be redefined).  
Over many years of working in the scientific software area, I have noticed that the "native 2D graphics libraries" are shallow in function when starting off on the wrong foot with inverted ys.  This is partly because the early departure from convention cuts off the graphics library developer from advanced, geometric theory.
Khan Academy teaches standard coordinates (y-up) in its Math lectures, and upside-down coordinates (y-down) in its Computer Science graphics lessons (based on JavaScript).  That's a confusing approach to be taking.  
