Answer: Secret Code #213

The secret message says:

LET'S PLAY

Letter by letter

Secret letter	B	G	H	K	O	V	Z
Real letter	Y	T	S	P	L	E	A

Decode it with Python

This program does the decoding for you. Change the secret and the code to crack other messages!

secret = "OVG'H KOZB"
message = ""

for letter in secret:
    if letter.isalpha():
        position = ord(letter) - ord("A")
        message = message + chr(ord("Z") - position)
    else:
        message = message + letter

print(message)

When you run it, it prints:

LET'S PLAY