If you notice on the NW pit, precisally on (9,7)-(10,6) floor, (to see them just click with the left button of your mouse on the floor) those two squares are allineated diagonally, and snakes can't move diagonally, so
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×just let you follow in there and then move diagonally and the snake will die
About the movement is like DooM said; watch the clock to understand better, sometimes he prefers moving vertical and other time horizontaly (every 5 turn). Of course even if he prefers vertical but you are right on his left he will chose to kill you
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There's not some other world out there where everything's gonna be okay.
There's just this one, just this rock.
-33th Skywatcher