Just a heads up, If you're a sudoku lover like me but aren't used to using words and that is slowing you down. You can actually change it to the numbers to make it easier on yourself and as long as the puzzle is solved it still counts for solving the word puzzle too!
If i remember correctly when you pause it you can check the number box and it'll change, i did it at the beginning of the puzzle so not sure if it'll change one your already doing or not.
I changed it to numbers and turned off the music (BGM) because it was all giving me a headache. Made my times go from over ten minutes down to 4 something!!
ALSO another thing i noticed about the puzzles: There is always a number sequences of 1-9 going from left to right or from top to bottom, I haven't got to the harder puzzles yet so they could mix it up more than that but so far I have never seen it go backwards into a countdown or in any other direction so if you figure out where that line is and input that information that gives A LOT of numbers (or letters) right off the bat! I have been doing the numbers but I'm going to guess and say it spells out the word if you left it on letters! I usually start there and then that gives me a lot of numbers to work with right away! Sometimes you might have to fill in a few numbers/letters to find that line but once you know what your looking for it seems to be pretty easy to spot!