On the Subject of Modern Cipher

The Roman warlord Caesar had his own personal way to encrypt his data. We could think about him as the father of the modern cryptography. But you are a qualified soldier so you won't have problems in decoding our message, don't you?

You are given an encrypted word. Decrypt it, write it in the second box and press OK to solve the module.
To decrypt the word start by finding the key.
Add every digit on the serial and then, referring to "Letter-Number Relation" below, follow the cases to find your word.
Keep in mind that if you have strikes*, you must add those strikes to the resulting key.

Case 01: The serial number contains a vowel:
Every letter of the word must be shifted backwards by the key
Keep in mind that if you go under the 0, the next number will be 25 because numbers go only from 0 to 25.
Case 02: The bomb contains more than 3 batteries:
Every letter of the word must be shifted forwards by the key
Keep in mind that if you go over the 25, the next number will be 0 because numbers go only from 0 to 25.
Case 03: There is a serial port:
If this is your first word, refer to Case 01, otherwise go on.
Add to the key the number of letters of the last word you decrypted, then proceed as in Case 01.
Keep in mind that if you go under the 0, the next number will be 25 because numbers go only from 0 to 25.
Case 04: None of the previous cases matches:
Add to the key the number of solved modules at the moment of the word generation then proceed as in Case 02.
Keep in mind that if you go over the 25, the next number will be 0 because numbers go only from 0 to 25.


*You want to add only the strikes that you have when the word is generated.

Letter-Number Relation



Letter Number
Q 0
W 1
E 2
R 3
T 4
Y 5
U 6
I 7
O 8
P 9
A 10
S 11
D 12
F 13
G 14
H 15
J 16
K 17
L 18
Z 19
X 20
C 21
V 22
B 23
N 24
M 25