something as trivial as 2D distance calculation
If its so trivial, I bet you feel really stupid for not being able to do it.
Oh and Bytes are often 1) the same size as an Int (in real memory tearms, less you have four of them in one type), 2) Slower than an int.
Also any good AI you would want the enemies to know how far they are from each other. So for 40 enimes (and you) thats 800 or so calculations