Comment by mintplant

I agree with B but disagree with A. Allowing dropping tiles outside of the word boundaries lets you arrange your "workspace" for thinking, like placing multiple candidate letters next to the spot where they might appear in the word. It could be useful to have tiles that are dropped within the word boundaries highlighted in some way to distinguish them, though.

My UX feedback: it isn't clear that the icon on the top-right opens up some instructions. Perhaps replace with the more standard question-mark in a circle?