Nurikabe: A Gentle Walk in the Hall of Giants

Question

This puzzle is a Nurikabe that is designed to be a gentle introduction to the genre, with a learning curve of progressively harder deductions. It is encouraged for first-time solvers and those who want to try learning the deductions necessary to solve these kinds of puzzles. It's also my first grid-deduction puzzle - I hope you enjoy!

Rules of a Nurikabe (paraphrased from here):

This is a Nurikabe puzzle. The goal is to paint some cells black so that the resulting grid satisfies the rules of Nurikabe:

• Numbered cells are white. (Think of them as "islands.")
• White cells are divided into regions, all of which contain exactly one number. The number indicates how many white cells there are in that region.
• Regions of white cells cannot be adjacent to one another, but they can touch at a corner.
• Black cells must all be orthogonally connected. (Think of them as "oceans.")
• There are no groups of black "ocean" cells that form a 2×2 square anywhere in the grid.

Now, here's the puzzle:

And here is the puzz.link solver, which lets you solve it online. I also made sure the image was MS Paint compatible.

(Beta-solved and tested by the incomparable crown, @bobble - thank you!)

Answer 1

Starting off by filling the 'easy' deductions with the 1s and 2s:

Next, we have to consider reachability:

We need to stretch the upper-left 6 as far as possible to avoid a 2×2, and then we can resolve the nearby 3 as well.

Now, an interesting deduction appears:

We can't have this red box fully shaded. But only one of those cells is reachable -- the top-right one, by the 6 clue. That will stretch out the 6 as much as possible, too.

Next,

look at the newly-created dot near the bottom. If it's taken by the 12, then the 3 must go downwards -- and now the wall between the 12 and the 3 is trapped, without any way to connect to the rest of the wall.

So that must be part of the 3 instead.

And finally:

The cell in row 5, column 9, must be shaded; if it's unshaded, then it must be taken by the 6, and that blocks off the top-right wall region. And with that, the puzzle is solved!