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Work in progress... UI Theme for Web, Qt and GTK. Colors will be user selectable (accent color, background tint).
If someone has an Idea on how to implement an editable combobox for HTML/CSS/JS that will not interfere with accessibility tools please chime in.
Currently not using any CSS framework, just a lot of CSS variables and calc functions. HTML is as clean as possible, currently I have to add a div around a dropdown (select) box to be able to add the down pointing arrow, all other UI elements are just label and input tags without any class attributes.
@SynAck@dunkelstern Dunno why, but the dark themed one reminds me a lot of the old Apple Aqua style. 
@SynAck for aqua it would need that shine layer on top. Totally doable but a bit over the top for me…