Perfect Square Sudoku

Perfect Square Sudoku is a Sudoku variant likely first proposed by Andrey Bogdanov for the Belarusian Puzzle Championship in 2010. In addition to the standard Sudoku rules, this variant introduces an extra condition: the pair of digits in any two orthogonally adjacent cells must form a perfect square (such as 16, 25, 36, 49, etc.).
This added restriction tightly limits which numbers may appear next to each other, creating highly structured grids and a distinctive style of deduction that blends arithmetic reasoning with classic Sudoku logic.

Rules

Fill in the grid with digits from 1 to 6 putting one digit per a cell. Each row, column and outlined area should contain every digit exactly once. Dots show all two-digit perfect square numbers reading from top to bottom or from left to right. Perfect squares numbers are 16, 25, 36, 49, 64, 81.

Click to see the answer.