Here you'll find everything you need to help you create your theme. If you have any useful tools, you can always add them below.
When developing your system, you'll want to be able to display effects without rebooting the whole system each time. To do this, plug in a keyboard and press ALT + F5. This will reload the theme with the latest additions, so you can see the result straight away.
If you apply a modification to your theme and it doesn't have the desired effect, you'll have a file in the system called themes.log, which records what went wrong. This file can be found in /recalbox/share/system/logs.
Here are a few tools you may find useful as you write all your theme documentation:
This site lets you select and convert colors to RGBA and Hexadecimal formats.
This site lets you optimize and clean up any SVG files you may have in your theme. This includes removing unnecessary elements such as comments from the software that saved the SVG in question as well as simplifying the code for the same result.