zotero/scss/components/_button.scss

//
// Button
// --------------------------------------------------

.btn {
	font: {
		family: inherit;
		size: inherit;
	}
	line-height: inherit;
	color: inherit;
	text-align: center;
	-moz-appearance: toolbarbutton;

	&[disabled],
	&.disabled {
		opacity: $btn-disabled-opacity;
	}
}

.btn-icon {
	.icon {
		svg, img {
			vertical-align: middle;
		}
	}
	span.menu-marker {
		-moz-appearance: toolbarbutton-dropdown;
		display: inline-block;
		margin-left: 4px;
	}
}