Code Golf: Clockwise Spiral

It's been a while (and everyone is well-rested after Advent Of Code!) so let's run another round of Code Golf.

Your task is navigating in a grid-like labyrinth in a clockwise spiral pattern. As it traverses the matrix, it collects characters, revealing a secret message.
Your challenge: find the shortest, most elegant code to decode this spiral cipher.
Input:
1. A multidimensional string array with comma separated characters (n x n)
2. Starting coordinates X and Y

Output:
The decoded message as a single string

Constraints:
1. 1 ≤ n ≤ 100
2. The starting position is always valid within the matrix
3. The matrix contains only printable ASCII characters

Example:

Input:

 matrix(1)="H,E,L"
 matrix(2)="R,L,L"
 matrix(3)="O,W,O"

Starting position: (1, 1)

Output: "HELLOWORL"

​

Note

• Use this code to check the solution length

Rules

1. The signature of the contest entry MUST be:

   Class codeGolf.ClockwiseWord
   {
   
   ClassMethod Solution(ByRef matrix, x, y) As %String
   {
       // Your solution here
   }
   
   }
   

2. It is forbidden to modify class/signature, including but not limited to:

   • Adding inheritance
   • Setting default argument values
   • Adding class elements (Parameters, Methods, Includes, etc).

3. It is forbidden to refer to non-system code from your entry. For example, this is not a valid entry:

   ClassMethod Build(f As %Integer)
   {
     W ##class(myPackage.myClass).test(a)
   }
   

4. The use of $ZWPACK and $ZWBPACK is also discouraged.

5. You can use this test case:

   Class codeGolf.unittests.ClockwiseWord Extends %UnitTest.TestCase
   {
       Method TestSolutions()
       {
           Set matrix($Increment(matrix)) = "H,E,L"
           Set matrix($Increment(matrix)) = "R,L,L"
           Set matrix($Increment(matrix)) = "O,W,O"
           Do $$$AssertEquals(##class(codeGolf.ClockwiseWord).Solution(.matrix, 1, 1), "HELLOWORL")
       }
   
       Method TestStartTopRight()
       {
           Set matrix($Increment(matrix)) = "A,B,C"
           Set matrix($Increment(matrix)) = "H,I,D"
           Set matrix($Increment(matrix)) = "G,F,E"
           Do $$$AssertEquals(##class(codeGolf.ClockwiseWord).Solution(.matrix, 1, 3), "CDEFGHABI")
       }
   
       Method TestStartMiddleRight()
       {
           Set matrix($Increment(matrix)) = "A,B,C"
           Set matrix($Increment(matrix)) = "H,I,D"
           Set matrix($Increment(matrix)) = "G,F,E"
           Do $$$AssertEquals(##class(codeGolf.ClockwiseWord).Solution(.matrix, 2, 3), "DEFGHABI")
       }
   
       Method Test1x1Matrix()
       {
           Set matrix($Increment(matrix)) = "A"
           Do $$$AssertEquals(##class(codeGolf.ClockwiseWord).Solution(.matrix, 1, 1), "A")
       }
   
       Method Test4x4Matrix()
       {
           Set matrix($Increment(matrix)) = "C,O,D,E"
           Set matrix($Increment(matrix)) = "U,C,H,G"
           Set matrix($Increment(matrix)) = "M,U,F,O"
           Set matrix($Increment(matrix)) = "S,I,F,L"
           Do $$$AssertEquals(##class(codeGolf.ClockwiseWord).Solution(.matrix, 1, 1), "CODEGOLFISMUCHFU")
       }
   
       Method TestStartBottomLeft()
       {
           Set matrix($Increment(matrix)) = "1,2,3"
           Set matrix($Increment(matrix)) = "8,9,4"
           Set matrix($Increment(matrix)) = "7,6,5"
           Do $$$AssertEquals(##class(codeGolf.ClockwiseWord).Solution(.matrix, 1, 3), "781234569")
       }
   
       Method TestAllSameCharacters()
       {
           Set matrix($Increment(matrix)) = "X,X"
           Set matrix($Increment(matrix)) = "X,X"
           Do $$$AssertEquals(##class(codeGolf.ClockwiseWord).Solution(.matrix, 1, 1), "XXXX")
       }
   }