Adventures of Lolo/Passwords

Passwords
Passwords are composed of a four-letter code, from a limited alphabet. The passwords are generated based on the level and follow a simple pattern.

Details
The passwords are actually base 16 numbers using the alphabet BCDGHJKLMPQRTVYZ. The password is divided into two portions; the left two digits and the right two digits. Starting from the initial password, add 1 to the left two digits, and subtract 1 from the right digits to generate the next level's password.

While you regroup within the 2-digit set, both of these portions are independent.