Ability to change themes

[Jopp-gh]

to write themes in css isn't difficult.
The point is rather:

• is theming even possible?
• where should I put my css file, what path? (linux ubuntu flavour, in my case)

Please no pitch black themes... I'm not a "night owl".
And here's a very, very simple and not perfect, but less hard b/w theming:

I tried to recreate $HOME/Documents/massCode/assets/index-BW1J4CAf.css without success. Here's my silly-simple code:

@layer theme {

    :root,
    :host {
        --color-bg: oklch(0.85 0 0);
    }
}

html.dark {
    --color-bg: oklch(0.39 0 0);
}

.cm-s-oceanic-next span.cm-comment {
    color: #889eaf;
}