misskey/src/client/components/form/form.scss

._formPanel {
	background: var(--panel);
	border-radius: var(--radius);
	transition: background 0.2s ease;

	&._formClickable {
		&:hover {
			//background: var(--panelHighlight);
		}

		&:active {
			background: var(--panelHighlight);
			transition: background 0s;
		}
	}
}

._formLabel,
._formCaption {
	font-size: 80%;
	color: var(--fgTransparentWeak);

	&:empty {
		display: none;
	}
}

._formLabel {
	position: sticky;
	top: var(--stickyTop, 0px);
	z-index: 2;
	margin: -8px calc(var(--formXPadding) * -1) 0 calc(var(--formXPadding) * -1);
	padding: 8px calc(16px + var(--formXPadding)) 8px calc(16px + var(--formXPadding));
	background: var(--X17);
	-webkit-backdrop-filter: blur(10px);
	backdrop-filter: blur(10px);
}

._themeChanging_ ._formLabel {
	transition: none !important;
	background: transparent;
}

._formCaption {
	padding: 8px 16px 0 16px;
}

._formItem {
	& + ._formItem {
		margin-top: 24px;
	}
}