Bubble Bobble Lost Cave

A lot of levels in the conversions were created specifically and are not in the arcade version. An Italian programmer, Aladar, did a comprehensive reverse engineering of the Bubble Bobble arcade code in order to port the best 100 of those levels to the arcade machine (the levels were selected and adapted by Aladar's collaborator. This is "Bubble Bobble Lost Cave".

Also, Bubble Bobble had part of the game logic running on a separate microcontroller with encrypted ROM, and it took almost 30 years until it was decapped, decrypted and emulated. This microcontroller is why most Bubble Bobble bootlegs suck. As part of Lost Cave result he also adjusted one of the bootleg ROMs so that the game's Z80 CPU implements all the original logic of the microcontroller faithfully.