Creating a circular matrix with one input

[deanhystad]

I like the snake reference.

>>>>>
    v
    v
    v
<<<<v

Start in the upper left corner and fill to the right until you can go no further. When you can go no further make a 90 degree left turn and fill until you can go no further.

That makes a really simple rule:
Go straight if you can, else turn left.

Of course the "if you can" and "turn left" are a bit more complicated.