How are the smoke trails from Treadnauts done?

I’m currently practicing for my portfolio and I stumbled upon Treadnauts. I find their smoke trails to be quite interesting, because I cannot figure out how they’re done technically. Sometimes they look like particles blending into each other and sometimes it just looks like one solid shape with a gradient.

I tried playing around with different particle settings, but I don’t think this was done with particles since they can blend into each other seamlessly?

Hi, it’s particles, but they use special shader for single transparency value. It’s like you turn on ZWrite for particle shader, but without bug with quads.

Thanks for the answer, but I don’t really understand what you said to be honest. I have a basic understanding of most nodes in Shader Graph (Unity), but I am still drawing a blank when I open it. I don’t even know how to start.

What do mean by single transparency value? I also don’t know what ZWrite is and don’t know about bugs with quads.

@Hovl Maybe it would help me, if you could explain to me what happens in the picture. Some of the trails in the background look like they’re just one grey value and then have some kind of alpha blend. The missile smoke in the bottom right looks like there’s also a gradient going on from white to grey and then alpha fade at the end.
Does each particle have a gradient so that it looks this smooth?

These are just particles. But using custom shader their opacity is not added.