It's a bit slow to use with a touchpad. I'd suggest being able to drag from any highlighted letter to an adjacent letter to add it (and more) to that word and m

It's a bit slow to use with a touchpad. I'd suggest being able to drag from any highlighted letter to an adjacent letter to add it (and more) to that word and maybe being able to drag from any highlighted letter (not vital for connectivity) 'inwards' to remove it (and more) from the set (where sensible). The whole delete-and-select menu is a bit clunky, in comparison. You can always highlight invalid words differently.