Welcome to this thread, For the curious peoples, this thread is for advanced assembly coding (.asm), because i do not know good this langage, in fact the machines langage. Since some times, i had thought make a sonic's rom hack with a lot of functionnalities, like many bosses, with very cool gameplay, that who could prove the rom hack would be cool for playing three times by day. When i want make the bosses and coding the enemies differences, i see i do not know really the assembly langage, the langage of the Megadrive (or Genesis in America). -For more information take a look below- My progress in Rom Hacking Since some days, i begun my "real" first rom hack, because before i had maked some rom hacks, but they are a little bad and i do not want to retry. I create my rom hack in the good path, i already changed the graphics of the enemies for like be in the next of Sonic 1 (this is i want to say through my rom hack story), but the background stay very bad, but i can modify it, so this is still not my issue. My issues Look that i want to explain to you: I want to make my custom bosses, and change some bosses, but i do not know how to good write in Assembly langage, so i modify the original bosses, and i stay in the same issue, because i want to put a first boss in the second level and the second boss in the final level. I would like know if we can code easily a boss or it is impossible or too hard. I need help for make a possible great rom hack in assembly (.asm) and realize that i want to do. Thank you very much.