\\(\mathbf{op}: \mathcal{C} \to \mathcal{C}^{op}\\) is a functor.

In short, it does nothing to objects but flips arrows around.

**Puzzle:** Prove that \\(\mathbf{op}: \mathcal{C} \to \mathcal{C}^{op}\\) is a functor.

In short, it does nothing to objects but flips arrows around.

**Puzzle:** Prove that \\(\mathbf{op}: \mathcal{C} \to \mathcal{C}^{op}\\) is a functor.