The only diffirence is that atan2 uses the first parameter to switch the output angle for you. And it does it more efficiently than you, Cybex, because there is no need at all to compile the whole trig math twice for each case. I could understand if you simply inverted the function, but noooo. But in the better case to determine why the function is included, inverting the angle manually would be doing something already done for you for no reason. Not to mention the Math functions are written in bytecode.