[SOLVED] HabPanel CSS/theme: incompatible browser [solved]

hello, i am running on a raspi3 screenly ose with a 7" raspi-display. unfortunately the habpanel config tells me that all themes are not compatible with this (screenly-)browser.
I would like to use the “Translucent” theme. Therefore I tried to achieve a similar display with the following css-code:

body, .container, .header, .dashboard-title, h2, .drawer, .menu li:not(.active) {
    background: white !important;

a {
    color: darkblue;

.box {
    background: rgba(0, 0, 0, 0) !important;
    background: lightgray !important;

After several attempts with different code I fail because i dont know which classes I have to overwrite with css …
can someone help me to make the backgrounds of widgets grey transparent?

This is the incompatible theme:

and this is the theme I want to have:

Nobody has an idea?

This is wrong, you can’t define multiple background attributes.
In the rgba function the last argument is the alpha value (transparency), so what you want is probably something like:

.header {
    background: none !important;
.box {
    background: rgba(0, 0, 0, 0.3) !important;