The challenge with indicating which rows and columns have been “completed” is that any “complete” sign would look like “this row is complete AND correct”, when in fact it may not be correct at all – it just happens to match the pattern indicated by that one row. I could work around that by using a more real-time checking system, but I don’t really want to go that route; it makes it too easy to cheese the puzzle by making guesses.
I’m definitely going to implement your idea about leaving dead cells unfilled. There’s really no reason why the player should have to mark each one.
Thanks anon