Pokemon Sacred Gold (Pokemon Heart Gold Hack) is a hacked version of a ROM hacker named Drayano, who also created many interesting hacked Pokemon versions on the GBA system. This time, inspired by Pokemon Heart Gold on the NDS system, Drayano continues to launch another unique version, but the style of all the versions he created has a certain similarity. There are no plot and map changes, participating in the game you will be adventuring in the vast Johto and Kanto regions, where your task is to challenge the Gym Leaders and finally to challenge the champions to become the new regional champion. What changes in this section is that the experience of the game becomes more charismatic, the balanced Pokemon cause the stronger types to drop their base stats and the weak ones to become stronger and more chosen. Battles also become more intense when opponents will always be level and will have up to six Pokemon to use. In addition, there are many new items added and modified old items, typically the TM will now suit more Pokemon, not just suitable for some types as before. And there are many other interesting things that I will let you discover during play.
More information
https://gbatemp.net/threads/pokemon-sacred-gold-storm-silver.327567/
