# [Jelly], <s>119</s> 114 [bytes]
### WHAM

    “ƭHGE94=ẠĊỴI>ạȧⱮṅƇṾ'Ñɦȥ⁴7?6ụ\ĖḂẆṾƇṗyZḣ&c%~Œ’ṃ“ |\_”s7;€“| |”µṚ“\/”y;µ€s6U4¦
    “ŒUỴ2,Ɠ’ṃ“|'-. ”s4µṪẋ7ṭµ€m€0s3ṚjЀ¢Y€Y

**[Try it online!]**

### How?

The general idea is to choose letters which have left-right symmetry with minimal character translation so as to (a) reduce the base in which the data may be encoded and (b) keep the "reflection" function small.

The letter `H` has left-right symmetry with no need for translation. The letters `W` and `A` also have left-right symmetry if the `/`s on the left become `\`s on the right. Unfortunately there are not four letters such letters.

Letters such as `O` introduce more characters, which increases the base needed for encryption making for a far larger number and hence more bytes.

`M`, however, only introduces the other slash - if the half rows for the `M` are stored in reverse *and* with the wrong slashes, the base is kept at four and a post-decryption, post-reflection reversal of just these rows puts everything right again (this is the `U4¦` in Link 1). This also means the character translation only needs to cater for `\` becoming `/` and not the other way around too (i.e. `Ṛ“\/”y;` rather than `Ṛ“\/“/\”y;`).


    “...’ṃ“ |\_”s7;€“| |”µṚ“\/”y;µ€s6U4¦ - Link 1: middle rows of blocks: no arguments
    “...’                                - base 250 number
         ṃ“ |\_”                         - convert to base 4 with digits [0-3]="_ |\"
                s7                       - split into sevens
                    “| |”                - literal "| |"
                  ;€                     - concatenate €ach
                         µ               - monadic chain separation (call that rhs)
                                 µ€      - for each r in rhs:
                          Ṛ              -     reverse r
                           “\/”y         -     convert any '\'s to '/'s
                                ;        -     concatenate with r
                                   s6    - split into sixes
                                       ¦ - apply to indexes...
                                      4  -   four (the M)
                                     U   -   upend
    
    “ŒUỴ2,Ɠ’ṃ“|'-. ”s4µṪẋ7ṭµ€m€0s3ṚjЀ¢Y€Y - Main link: no arguments
    “ŒUỴ2,Ɠ’                               - base 250 number
            ṃ“ -|.'”                       - convert to base 5 with digits [0-4]="' -|."
                    s4                     - split into fours
                      µ                    - monadic chain separation (call that lhs)
                           µ€              - for each l in lhs:
                       Ṫ                   -   tail l
                        ẋ7                 -   repeat (the tail) seven times
                          ṭ                -   tack to l
                             m€0           - reflect €ach
                                s3         - split into threes
                                  Ṛ        - reverse
                                      ¢    - call last link (1) as a nilad
                                   jЀ     - join mapped over right
                                       Y€  - join each with newlines
                                         Y - join with newlines
                                           - implicit print


[Jelly]: https://github.com/DennisMitchell/jelly
[bytes]: https://github.com/DennisMitchell/jelly/wiki/Code-page
[Try it online!]: https://tio.run/nexus/jelly#@/@oYc6xtR7urpYmtg93LTjS9XD3Fk@7h7sWnlj@aOO6hztbj7U/3LlP/fDEk8tOLH3UuMXc3uzh7qUxR6Y93NH0cFcbUA6kYHpl1MMdi9WSVeuOTnrUMPPhzmagsQo1MfGPGuYWm1s/aloD5Nco1AC5h7Y@3DkLyIvRB3IqrQ9tBUoWm4WaHFrGBRQ9OikU6AAjnWOT4cbUqOvqKYDMMQFpXfVwV7f5w51rwfpygdig2BhoYNbhCUD2oUWRQDLy/38A