When I first tried a Number link puzzle a few years back I didn’t like it at all – it wasn’t immediately clear how to go about solving it, and I didn’t see how I’d ever find it fun. However jump forward to now and I find them really enjoyable, perhaps because it usually is hard to know how to solve them and so you need some fresh thinking each time you try one.

It’s not the only puzzle I’ve had this experience with. There’s a box-shading puzzle called Heyawake that I found horribly mechanical and tedious when I first tried one, probably because at that point I could only tackle the easy ones and so mainly I got stuck when I failed to spot where I could directly apply a solving rule. However a couple of years ago I tried it again and it soon turned into one of my absolute favourites, although it hasn’t quite pushed Nurikabe off its crown of being my personal number one.

It works in reverse too, however.  I used to really enjoy Filomino puzzles, but now I mostly find them rather dull – I think that once you get good at certain puzzles you hit a natural wall in difficulty where making them any trickier without requiring what is essentially just guesswork is a real challenge, so you find most puzzles mostly easy.  In a great puzzle (like Sudoku), you’ll always find some puzzles tricky no matter how knowledgeable you get, but not all puzzle types behave so gracefully.

The point of all this is that Number link is one of those puzzles that – for me at least – always presents a challenge, and makes me think anew each time I try one. And because it can be infuriatingly tricky it’s also capable of giving me a great deal of satisfaction when I do solve a puzzle.

The Number link examples I’ve posted so far have been pretty easy, so I thought I’d post a few more that were a bit harder. All of these have at least a couple of obvious moves, so it’s certainly possible to make trickier 10×10 puzzles than these, but they do present at least a bit more of a challenge.  I’ve arranged them by what I considered increasing order of difficulty, but you may disagree, depending upon how inspired you are as you tackle each puzzle!

The rules are simple: connect each number to its identical partner using only horizontal and vertical lines.  Only one line may pass through a square, so lines cannot cross or overlap.  There is only one solution.  In all of these puzzles the unique solution also uses every square. Both of these last two facts are very useful in narrowing down possible solutions!  Take a look at my previous posting for an example solution.

Good luck!

Edit: The first version of this post included a puzzle (number 2) that had lots of different solutions that didn’t use all squares – I’ve now replaced it with an alternative puzzle.   See comments.