`and()` is for combining them, so ``` content_box ...
# tornadofx
r
and()
is for combining them, so
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content_box {
    and(button) {
        backgroundColor += c("transparent")
    }
}
would become
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/* No space, this applies to elements with both classes, not buttons inside content boxes */
.content_box.button {
    -fx-background-color: none;
}