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Let us step back from what we have done before and spend some time on user interaction - at least they should be able to walk over listed items which means we somehow should accept navigation commands. For such a purpose we can use Shifter since we use Scrolling List.
But how we get an actual user interaction? Since we operate in command line we can accept a single character from standart input:
Following VIM convention for navigation, let's bind J and K lowercase letters to vertical movement - we do it by inspecting received ASCII character and designating Shifter variants:
Challenge: add aliases of navigation keys.
Since World is functor we can compose those expression together:
If user inputs something except J and K computation wouldn't proceed since we don't get a command in this case. Good news is that we can torture user to repeatedly ask for a proper input until we get one:
Challenge: use default behaviour - so it tries to match for a key only once.