Sometimes it's difficult to read partly completed vertical answers especially if they are long.
Would it be possible to Display the partly completed word horizontally somewhere when clicked on?
My first idea was below the name and author of the crossword at the bottom of the window but anywhere would do.
You could also make it a preference setting to display this behaviour.
E.G. say the answer was HORIZONTALLY and you only had the H, R, O, N, L , L, Y from other answers the display would show : H_R__ON__LLY using an underline for each unknown letter.