Let's be real, Pokémon Heart Gold and Soul Silver is one of the best games ever made, it took the franchise to a whole new level thanks to its quality of life improvements and the addition of a new screen via the Nintendo DS hardware. Have you ever imagined what that game would look like on the GAME BOY Advance?
Well, a ROM hacker known as @rahtak has created just that, and it was officially released on the 26th July over on HackDex, free to explore and try if you have your Pokémon Emerald ROM file ready to aptch (which is the legal way of using/downloading ROM hacks). These ROM hacks can be used with real hardware, mGBA emulator and Lemuroid, alongside Delta and Afterplay.

According to Rahtak: "It is a Johto-focused expansion hack based on an unofficial expansion port of Heart and Soul. It delivers a traditional Pokémon adventure through an expanded Johto region featuring fresh tilesets, boss battles, multi-ability postgame mechanics, battle facilities, and extensive quality-of-life updates".
Adding a wide range of additional features, such as post-game content, temp improvements, achievements, new boss Pokemon, hidden grottos, more legendaries, DS features, and a whole lot of extra customisations. Here's the full list:
ROM Hack Features:

- Play through the traditional Pokémon adventure in the main game and experience learning multiple abilities in the postgame.
- Various battle tempo improvements, such as combining stat up/drop messages into one, and playing them while the stat animation happens.
- Main game and postgame battle facilities with Pokémon from all generations! Factory accessible after Gym 3!
- Hidden Grottos, which contain rare items and Pokémon, resetting daily
- Boss Pokemon, some legendary fights have multiple health bars and are more powerful, but you are guaranteed to catch them with any ball once defeated
- Achievement system with over 100 trophies to chase, including milestone rewards!
- 9 starters to choose from with new Mega Evolutions for starters that are missing them (Typhlosion, Meowscarada, Primarina)
- Fresh new tileset for the entirety of Johto
- Title Defense system: No longer will you face only the same champion at the end of E4.
- All mega evolutions are available; megastones have been turned into type-generic stones.
- Rocket Arcade, where you win money instead of BP
- Multiple legendaries to find in the main game and postgame!
- Fishing for items, including IV-raising feathers!
- Many HGSS features, such as Cameron the Cameraman, Buena's password, Pokégear, and Rock Smashing for fossils, make their return!
- Unique battle frame colour for shiny Pokémon
- Music resumes from where it left off after battles instead of starting over
- Multiple pages of options to customise your playthrough style
- Various quality of life features and gameplay feel improvements
For those new to the ROM hack scene, acquiring and keeping track of these is fairly easy. A new website known as HackDex allows you to upload your own legally sourced ROM hack, and then legally patches it (or hacks it if you're cool) and turns it into a newly developed game, allowing you to experience awesome ROM hacks swiftly and safely. You can download Pokémon SoulGold here.