The Idea

We've done matrix spirals before, and full rotations, and even diagonal
rotations,
but not, as far as I can find, snake rotations!

What is a snake rotation?

Imagine the rows of a matrix snaking back and forth, with dividers between
them like the dividers of long queue:

    +--------------+

      1  2  3  4  5|

    +------------  |

    |10  9  8  7  6|

    |  +-----------+

    |11 12 13 14 15|

    +------------  |

     20 19 18 17 16|

    +--------------+

Now imagine rotating these items by 2. Each item advances, like people moving
in a line, and the items at the end spill out and return to the beginning:

    +--------------+

-->  19 20  1  2  3|

    +------------  |

    | 8  7  6  5  4|

    |  +-----------+

    | 9 10 11 12 13|

    +------------  |

<--  18 17 16 15 14|

    +--------------+

If there are an odd number of rows it will exit from the right, but still wrap
to the beginning. For example, here's a 3 rotation:

    +--------------+

      1  2  3  4  5|

    +------------  |

    |10  9  8  7  6|

    |  +-----------+

    |11 12 13 14 15

    +--------------+





    +--------------+

-->  13 14 15  1  2|

    +------------  |

    | 7  6  5  4  3|

    |  +-----------+

    | 8  9 10 11 12  -->

    +--------------+

A negative rotation will take you backwards. Here's a -2 rotation:

    +--------------+

<--   3  4  5  6  7|

    +------------  |

    |12 11 10  9  8|

    |  +-----------+

    |13 14 15  1  2  <--

    +--------------+

The Challenge

Your function or program will take 2 inputs, in any convenient format:

• A matrix


• A integer (positive or negative) indicating how many places to rotate it.

It will return:

• The rotated matrix

Notes:

• Code golf. Fewest bytes wins.


• Matrixes need not be square, but will contain at least 2 rows and 2 columns


• Positive integers will rotate row 1 toward the right


• Negative integers will rotate row 1 toward the left


• You may reverse the meaning of positive / negative rotation numbers, if convenient


• The rotation number can be larger than the number of items. In that case, it
  will wrap. That is, it will be equivalent to the number modulo the number of
  items.


• The matrix will contain only integers, but it may contain any integers,
  including repeats

Test Cases

Format:

• Matrix


• Rotation number


• Expected return value

4 5

6 7



1



6 4

7 5

2  3  4  5

6  7  8  9

10 11 12 13



-3



5  9  8  7

12 11 10 6

13 2  3  4 

8 8 7 7

5 5 6 6



10



5 5 8 8

6 6 7 7

Jelly, 10 bytes

UÐeẎṙṁ⁸UÐe

A dyadic Link accepting the marix on the left and the rotation integer on the right (uses the reverse meaning of positive / negative)

Try it online!

How?

UÐeẎṙṁ⁸UÐe - Link: matrix of integers, M; integer, R

 Ðe        - apply to even indices of M:

U          -   reverse each

   Ẏ       - tighten

    ṙ      - rotate left by R

     ṁ     - mould like:

      ⁸    -   chain's left argument, M

        Ðe - apply to even indices of M:

       U   -   reverse each