Sooner or later, if you're developing multi-platform games, you'll need to understand the different coordinate systems that are involved.
In Moai SDK, we have at least three coordinate systems that are important to remember and to make good use of.
This is the coordinate system attached to your window. You will typically have to deal with it when receiving mouse or touchscreen input. You might also use it to design your GUI. If you ever experience any strange behavior when clicking, always double-check that you're correctly transforming input coordinates to world or even model coordinates.
This is the coordinate system that you define when setting the scale for the viewport, and is the ...