This simulator runs AVR assembly language code (particularly as taught in Sydney University ELEC1601). It is a tool to help show what happens inside the hardware of a computer so that a more comprehensive understadning of assembly language can be gained.
Inspiration has been drawn from others such as https://schweigi.github.io/assembler-simulator/ and http://daniel3735928559.github.io/jsavr/demo.html.
If you wish to write AVR code with a code theme there are a few options. One is to use the included .xml file in Notepad++ (for windows users only). Another is to use the 'AVR Support' extension in VS code, which runs on .asm files.
This code can then by copied across into the web page and run as normal.
Try it at: https://jonopriestley.github.io/avrsim/