There are a number of numerical methods for finding the square root of a number. Due to the irregularities in rounding, consider implementing an allowance for a margin of error something to the magnitude of 1e-6, as in their square root must be within 1 one millionth of the actual value. Good luck!

Because the grid is reference type, each run is not independent of the last as you are passing in the same grid for many tests. As such the tests will fail on subsequent runs if the data therein is manipulated unless the programmer starts by making a local copy of the grid on each run. This is out of spec. I suggest changing your testing methods such that every grid tested has a unique reference. It is a cool problem otherwise.

This Kata is ranked too low. In order to solve this efficiently you must be able to reason through many nested branches, loops, lists, and dictionaries.

A diagram might help people visualize how to solve this problem geometrically. Otherwise this is by far the greatest Kata of all time!