Odd method of calculating PI in C - Explainations?

From:
Obfuscated C Code

We find:
http://www.cise.ufl.edu/~manuel/obfuscate/pi.c

To check the output online:
C code - 21 lines - codepad

Yes, the program as it is pasted there gives a poor approximation, however... the accuracy of the calculation increases as the circle diameter is increased. I've stared at this for a little while but can't seem to make sense of what's actually going on, do any of you have insight in to the program flow and what the statements are executing?

The International Obfuscated C Code Contest
Find the entry, read the notes.

Originally Posted by since

I've stared at this for a little while but can't seem to make sense of what's actually going on, do any of you have insight in to the program flow and what the statements are executing?

I'm not much for math, but the flow of this is pretty straight forward I think. The pattern of the shape is irrelevent, of course. Look at the #define _

Never mind, explanations are starting to finally show up here;

http://www.reddit.com/r/programming/...beautiful_way/

Originally Posted by since

Never mind, explanations are starting to finally show up here;

http://www.reddit.com/r/programming/...beautiful_way/

I had all of it but the punchline:

It's F>0 for the first _ of each line, -F for each _ after that.

So F gets decremented 202 times, but OO only 16.

It's a shame however the shape doesn't actually represent a circle. In the end it cheats.

Still, nicely done. I couldn't see it, until I read how it was done.