We don't have rules specifying what you can change in the code, you are free to change whatever you want. These rules only affect how you release the mod when finished, and should be followed to make sure your account stays secure and the GPL license followed.

Modding Rules

1) PLEASE don't include your powder.pref file if you post a Powder Toy mod! Any smart person can take this file and login as you in an instant. The same applies even if you're not posting a mod. This has happened many times before on accident, and the results are never pretty. If we catch you posting something with this in it, the link will be deleted until you remove this file.
2) Always post the source code for your mod alongside the link to your mod. Otherwise it will similarly be deleted, since no one can tell if there are viruses or other malicious code inside. This is because The Powder Toy is licensed under the GNU Public License (GPL). This means that it is required by copyright law to release the complete source code for all public releases you make.
3) Do not upload viruses or malware. This should be obvious, but some people have uploaded suspicious links with no source code, that seem to cause large annoyances to anyone who runs the program. If we can't tell if it's a mod or not, the post will be removed, and you may be banned. Legitimate instances of TPT which include code deemed to be malware will also be removed.
4) Do not post mod announcements. These are threads that announce a mod that will be released in a year or months from the thread. They may also ask for suggestions. Most of these never end up getting released for a few months, or ever, and just give false hope to the people who think it's real. If you want suggestions, there is the feedback forum, and a mod suggestion thread. You can post these threads if you have proof you have started (ex. Github commits, or a few elements made)
5) Do not post lua scripts or ask for help with lua scripts in this subforum. No matter how much like a mod it is, it still belongs in the Lua scripting subforum
6) Do not use revenue sharing ad sites or excessively ad-filled hosting sites to host your mod downloads. This notably includes mediafire, as the ads there can be tricky and have confused users into downloading the wrong thing in the past.

One way to guarantee compliance with all the above rules is to have your mod built automatically with Github Actions and hosted on my server. For more details, read this thread

Added rule 5, don't post lua scripts in this section.