Circular Matrix Spiral

[
  [
    1,
    2,
    3
  ],
  [
    8,
    9,
    4
  ],
  [
    7,
    6,
    5
  ]
]

[
  1,
  2,
  3,
  4,
  5,
  6,
  7,
  8,
  9
]

Explanation. Starting from top-left, we first move right across the top, then downwards along the right column, then left across the bottom row and finally upwards along the left column.

[
  [
    1
  ]
]

[
  1
]

Explanation. The matrix has only one element, so the spiral is simply that single element.

[
  [
    1,
    2
  ],
  [
    4,
    3
  ]
]

[
  1,
  2,
  3,
  4
]

Explanation. The spiral order begins at the top-left, moves right, then downward, and finally left.