1. Preparation and Tools:
* ROM: You'll need a clean, unedited ROM of the Pokémon game you want to modify.
* ROM Hacking Tools:
* A Hex Editor: This allows you to directly edit the ROM's raw data. Popular options include HxD, XVI32, and 010 Editor.
* A Disassembler: This tool translates the game's machine code into human-readable assembly language. Popular options include IDA Pro and Ghidra.
* A Scripting Tool: There are various tools specifically designed for Pokémon scripting, each with its own strengths and weaknesses. Popular options include:
* AdvanceMap: For Game Boy Advance (GBA) games.
* PKHeX: For multiple Pokémon games, including Generation 3, 4, and 5.
* Pokémon Essentials: For creating your own custom Pokémon games.
* Advanced Scripting Engine (ASE): For Game Boy Color (GBC) games.
* Documentation: You'll need to find documentation for the specific Pokémon game you're working with. This can include:
* ROM Maps: These show the layout of the ROM's data, making it easier to find specific locations.
* Script References: These provide explanations of the game's scripting commands and their usage.
2. Understanding the Game's Scripting System:
Each Pokémon game has its own unique scripting system. You'll need to learn how the scripts work, including:
* Script Commands: The specific commands used to control game events, character interactions, and other aspects.
* Script Structure: How scripts are organized and how they interact with each other.
* Variables and Data: How variables are used to store information and how data is accessed.
3. Identifying Script Locations:
You'll need to find the specific locations in the ROM where the game's scripts are stored. This often involves:
* Searching for Known Script Markers: Many games have specific markers that indicate the start of a script.
* Using Disassemblers: Disassemblers can help you identify the parts of the code that correspond to specific game events.
4. Writing the Script:
Using your chosen scripting tool, you'll write the script that implements the changes you want to make. This may involve:
* Adding New Events: Implementing new events, like a new encounter with a Pokémon, or a new dialogue with an NPC.
* Modifying Existing Events: Changing the dialogue, actions, or outcomes of existing events.
* Creating New Features: Adding new features, like a new menu option, a new battle mechanic, or a new item.
5. Placing the Script:
Once the script is written, you need to place it in the correct location in the ROM. This may involve:
* Inserting the Script: Directly inserting the script into the ROM at a specific location.
* Creating New Script Blocks: Creating new blocks of data in the ROM to hold the script.
* Remapping Existing Script Blocks: Modifying the game's script pointers to reference your new script.
6. Testing and Debugging:
After adding the script, you need to thoroughly test it to ensure it functions as intended. This may involve:
* Playing the Game: Testing the script in-game to see if it works as expected.
* Debugging Tools: Using debugging tools to identify and fix any errors in your script.
* Fixing Glitches: Addressing any bugs or glitches that may arise from the script.
Important Considerations:
* ROM Hacking is Complex: Learning the basics of ROM hacking takes time and dedication.
* Backup Your ROMs: Always make backups of your original ROMs before editing them.
* Legal Issues: Modifying commercial game ROMs for personal use is generally acceptable, but distributing them commercially or without permission is illegal.
Resources:
* Pokémon ROM Hacking Communities: Join online communities for Pokémon ROM hacking.
* Tutorials and Guides: Search online for tutorials and guides specific to the game you're working on.
* ROM Hacking Forums: Seek help and advice from experienced ROM hackers.
Remember, ROM hacking can be a rewarding experience, but it requires patience, persistence, and a willingness to learn.