Calculating degrees between 2 points with inverse Y axis

Question

I\'m creating a simple 2D game in javascript/canvas. I need to figure out the angle of a certain object relative to my position.

So: say I\'m at (10,10) and the object i

Answer 1

In HTML5 canvas the origin is the top left corner hence the y axis grows from top to bottom. So regardless of wherever you are on the unit circle to calculate the angle of point A to the center(C) you should in fact do like

angle = Math.atan2(Cy-Ay,Ax-Cx)

and you will get your result in the range of [-π, π].

I have no idea why they haven't made the canvas origin the bottom left corner.