Custom modification to built-in cards (energy-distribution-card)

I’m quit new to homeassitant but familiare to programing. My attempt is to adapt the bulid in energy-distribution-card for my needs. My hope was to find the source code of that card in the system files, make a copy and “implement” it as an custom card. I read that article: Custom Cards | Home Assistant Developer Docs

But doesn’t seem to be that easy. I just fount the energy-distribution-card.ts in the repsitory. As I understood I can’t use that directly for creating an custom-card.js…

My questions: Is the sourcecode of the inbuild cards anywhere in the systemfiles as an *.js file I could more easily start with? Or any suggestions on how to do such an copy and modification?

Thank’s a lot, Markus

I’d be interested as well. I found a modification of the original energy-flow-card here: GitHub - ulic75/power-flow-card: A power distribution card inspired by the official Energy Distribution card for Home Assistant

But I am not sure what kind of development environment I’d need to setup and use in order to modify that card further (I would like to replace gas and water consumption by other appliances (heat pump and electric vehicle)).

Basically I would like to create a better looking and “behaving” version of the “tesla-style-solar-power-card”.

Looking at the JS source code it would seem to not be a huge thing to replace those with my appliances, only thing I’m struggling is to find out how to set up a proper development environment and import that github repository to actually build the JS that should “fall out” when building it.