Gadget-ResponsiveStyle.css

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/* Responsive CSS applied to both desktop and mobile */

/* Mobile phone */
@media all and (max-width: 719px) {
	/* Echo extension */
	.mw-echo-ui-notificationItemWidget-content-actions-buttons {
		font-size: 10px;
	}

	/* User board */
	.user-board-message {
		width: auto !important;
	}
	.user-page-message-form textarea {
		width: 100% !important;
	}

	/* Template:Ref/List */
	.reflist {
		column-count: 1 !important;
	}

	/* Template:Notice */
	.notice {
		min-width: 0 !important;
		max-width: none !important;
	}
	.notice-wrapper {
		width: auto !important;
		display: block !important;
	}

	/* Hub pages */
	.hub-body {
		display: block !important;
	}
	.hub-body-col {
		width: auto !important;
		max-width: none !important;
	}
	.hub-body-box {
		margin-left: 0 !important;
		margin-right: 0 !important;
	}
	.mobile #hub-contents {
		display: none !important;
	}
}

/* Desktop/tablet */
@media all and (min-width: 720px) {
	/* User profile */
	#user-page-left > .profile-info-container > div {
		width: 50%;
		float: left;
	}
}

MediaWiki:Gadget-ResponsiveStyle.css