Suppose we are talking about reflections in 2D, and let's suppose that hypothetically I have something like a weistrass function with one side completely reflective

[![enter image description here](https://i.stack.imgur.com/B1DPu.png)](https://i.stack.imgur.com/B1DPu.png)

How would light reflect of it's surface if we shot a beam from above to the curve (at any point)?

This may seem like a trivial question, but it gets complicated as soon as you realize since the function is not differentiable, there is no clear tangent line approximation we can talk about and hence no normal at a point. So, it's no longer clear how to apply snell's law of reflection.