Well that was, very simply, incredible. The basis for the game (sum/product of rows/columns) isn't new, but I have yet to see a computer game of it, personally. And this was very cleanly done without overwhelming the user (okay, the multiplication sums get quite high, but other than that). Definitely appreciate the locking numbers and rows feature, as well as, of course, dark mode. Very well done, has been added to my favourites.