Nurikabe: Five Below

Question

This puzzle is another one of my Nurikabes, and this time it's a smaller one made entirely of pieces that are 5 or less. Perhaps you can tell that making puzzles in this genre is slowly becoming my thing! As always, I hope you enjoy.

Rules of a Nurikabe (copied from my previous puzzle):

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, the puzzle:

And as always, a spiffy puzz.link solver if you would like one.

Answer 1

COMPLETED GRID

REASONING

After the initial obvious deductions:

Start in the lower right corner. R9-10C9 are both shaded, meaning one of R9-10C8 must be unshaded. All of the pieces are small, so this must be blocked by the 3 in R8C9. The grid thus far:

To the left:

The 5 is hemmed in at left, so R6C3 must be in its region. This region could continue down to R7C3, but is blocked any further by the 3, so we must also have R6C4 in this region as well. This forces R7C4 to be shaded.

In the bottom middle, one of R9-10C6 must be unshaded, and in the region with the 3 in R10C5. If R10C6 is shaded, then R9C5 must be shaded, which would block the 3 in R8C4 from completing...so we must have R10C6 unshaded, and the exact same argument shows R9C5 must be shaded. The grid thus far:

Middle right:

The 2x2 R6-7C7-8 must have an unshaded square, and the only region that can reach it is from the 4 in R6C10...this forces the 4 region to extend over R6C8-10. which then forces the 2 region on R4C8. Looking slightly lower, we see the 2x2 R7-8C6-7 can only be reached by the 3 in R8C4, which forces the entire bottom part of the grid. The grid thus far:

In the middle:

The 2x2s R6-7C5-6 and R6-7C6-7 each need an unshaded square, and only the 5 and 4 in row 6 can reach. Easy fill-ins give us the middle of the grid:

Finishing up:

R2-3C4-5 can only be reached by the 2 in R1C4, which forces R1-3C3 to all be shaded, and only one cell in R1-3C2 can be shaded, so it must be R2C2. Finally, the upper right corner must be unshaded, otherwise it would be blocked.