Nurikabe Solving Hints
Although we don't currently have a magazine of nurikabe puzzles, it certainly fits the bill for a future candidate as it is both a Japanese puzzle and one that is particularly hard to come across. And we have loads of other great puzzle magazines for you to enjoy!
This is in no doubt partly because it is very hard to create nurikabe puzzles automatically, or more precisely to make nurikabe puzzles that are interesting if they are not hand made. In this guide we look at a small nurikabe puzzle to illustrate the basic principles you need to employ to solve these interesting logic puzzles.
In nurikabe, there are islands (denoted by numbers) floating in a sea of water (cells which will be coloured in). The sea must be connected so that you can move from any piece of sea to any other piece of sea, and must not contain any regions that are 2x2 (or larger). The islands may not touch each other horizontally or vertically, they must be true islands. Each island must contain the number of cells stated, including the cell that contains the number, and every island that exists in the solution has a single cell revealed at the start of the puzzle (each island may only have one number in it).
So, how to solve nurikabe? Look at the puzzle to the right. We know that each '1' must be surrounded by water horizontally and vertically since islands cannot touch, and since those islands only have one cell we know they contain no other cells.
We now have this position above. The next simple rule is remembering that all the water is connected. This means the second cell in the final column of the puzzle must also be water to enable the first cell in the final column to come out and join up the rest of the ocean.
We can then use the intuitive rule that the two's marked in the puzzle only have one other cell that could possibly be part of those islands. Filling in around these gives us this position (using a dot to mark additional cells within an island):
This just leaves us with the '3' island to work out. We know that one of the two cells at the end of column three must be part of the island, but not both. If neither were, there would be a 2x2 of black cells which is not allowed. If both were, then there would be a 2x2 block of black above the 3. So the cell above the '3' must be filled. Which of the other cells is? Well, if it were the one a cell to the left and a cell up from the 3, then that would isolate the black sea at the bottom left of the puzzle, which is against the rules. Therefore it must be the cell next to the 3, enabling the sea to come out, and the puzzle's unique solution is found:
And that's it, the end of our look at the simple rules that can be used to solve a nurikabe. The other rule you may need sometimes is to work out that no island can reach a particular cell, and therefore that it should be filled with ocean. Whilst a quick and useful way of working out how to progress with the puzzle, you usually don't find yourself needing that rule much apart from with fairly dull computer generated puzzles; most hand made nurikabe will require the other rules outlined above in preference to this one.
So that's nurikabe. Why not now purchase a puzzle magazine from one of the great selection of puzzles we have here at Puzzle Magazines?
Read more Puzzle Strategy Tips on a range of different puzzle types.
Try A New Puzzle...Sandwich Sudoku Rules
A lovely sudoku variant, sandwich sudoku gives you hints around the edge of the grid as to the location of the 1 and 9 in each row and column. This video explains the rules so you can have a go at this fun but tricky variant...
If you'd like to try this puzzle before watching the video then you can do so here: Sandwich Sudoku Puzzle