As the only other review was a bit negative, I wanted to provide my take. I have completed about 10 of these puzzles, all without paying for hints. While these definitely are not beginner level, they are not unreasonable in difficulty in my opinion. They may be considered unreasonably large. But you have a whole week to do them. They probably take me about 45 min to an hour. As the other review mentioned, there is no undo button. So you are forced to actually figure things out and can’t guess and check. Which I mostly like. It is only a problem if you accidentally tap something and can’t figure out where. And if you do have a mistake, you probably end up starting all over. Which to me just adds an element of challenge, but I understand may not be for everyone. And the other review complained that there were not different colors when you start a new line. With a puzzle this large, different colors are not reasonable as there are not enough distinct colors available. You would have to repeat colors, making them all but useless. Good news is I have yet to have any need to follow a loop all around the ball. The only times I have used the single loop rule have been small loops that are easy to see. So it has not been an issue. These are my favorite slitherlink and I look forward each week to a new puzzle

Really hard, took me a couple days to

Good game, great and intuitive interface, but there’s no way to undo moves which means you can’t try options and then back out. Also, other slitherlink apps color the lines that are connected a unique color so it’s easy to avoid closed loops. This version, instead of giving you useful features, asks you to PAY for a measly few hints without which solving the puzzle is overly difficult. Money grab! I’d rather have a few ads and more features. Uninstalled.