Differences From Vanilla

Vanilla for Soulgold means Pokémon Emerald, because Emerald is the ROM it patches. That matters more than it sounds: a Johto game has been rebuilt inside Emerald's engine, so some of what looks like a change is really the region being swapped out from underneath a familiar baseline.

What changed, by the numbers

Comparing every shared species against Emerald's own data:

Two things stand out. The stat pass only moves in one direction -- nothing in Soulgold is weaker than its Emerald counterpart, but 30 species are stronger. And the largest single bucket is ability slots, which is where innates and the mega work live, not the type chart.

The hack's FAQ adds two rules that the numbers do not show: no types change during the main game (the edits you do see are minor and postgame-relevant), and movepool changes exist mostly as extra late-game options rather than wholesale rewrites.

The shape of the game

Johto, with new tilesets across the whole region, expanded areas and biomes, and Pokémon from every generation available in battle. The main story is Johto through its eight badges. The game defines 16 badge flags and carries Kanto Leaders from Brock through Blue, plus Kanto maps including Cerulean City, Cerulean Cave and Viridian City Gym, so postgame Kanto content exists even though the hack's FAQ describes the project as pure Johto focus. Verify it in-game rather than trusting either source alone.

Systems you will feel immediately

• Tempo changes. Stat-up and stat-drop messages combine into one and play during the animation, HP drains simultaneously, the battle intro is faster, and there is a shortcut to Run.
• Level caps as soft caps. Experience gain is sharply reduced once a Pokémon hits the current cap instead of being blocked, so overlevelling is discouraged rather than forbidden.
• Options, plural. Multiple pages of settings decide how the run plays, including Hard mode's double Gym battles.
• Innates. Extra passive abilities that unlock in the postgame as a second progression track. They can be forced on early in Elm's lab, with the hack's own warning that it unbalances the game.
• Title Defense. The Champion you face at the end changes instead of being the same trainer every run.
• All megas available. Every mega evolution is in, and mega stones are type-generic rather than species-specific.

Things to go find

• Hidden Grottos reset daily and hold Pokémon with at least two perfect IVs and their Hidden Ability. The Beckoning Bell from the Battle Factory lets you reroll a Grotto on demand.
• Boss Pokémon. Some legendary fights use multiple health bars and hit harder, but you are guaranteed to catch them with any ball once they are beaten.
• Achievements. Over 100 trophies with milestone rewards attached.
• HGSS features. Cameron the Cameraman, Buena's password, the Pokégear, and rock-smashing for fossils all return.
• Battle facilities in both the main game and the postgame, with the Battle Factory accessible after your third badge. The Rocket Arcade pays out money instead of BP.
• Fishing for items, including the feathers that permanently raise IVs.
• Nine starters with new megas for the ones that were missing them, including Typhlosion, Meowscarada and Primarina.

Quality of life

Shiny Pokémon get a unique battle frame colour, music resumes where it left off after a battle instead of restarting, and the expanded options pages cover everything from battle UI to run rules. Day and night drive encounters, so the clock matters.

Where to go next

• Getting Started with Soulgold for the practical first hour
• Walkthrough & Progression Guide for badge order and caps
• Soulgold FAQ for the short answers