Twisting has the effect of adding 1:

x \to x + 1

Turning transforms any number into the negative of its reciprocal:

$x \to - \frac{1}{x}$

Take a look at this video:

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Starting at zero (with both ropes parallel), what would you end with after the following sequence of moves:

Twist, twist, twist, turn , twist, twist, twist, turn , twist, twist, twist, turn .

What sequence of moves will take you back to zero?

You may want to take a look at More Twisting and Turning after this.