youtubeとニコニコ動画でCSSぶっこんでシネマモードを実現するUserScript　ダブルクリックで切り替え

youtube_nicovideo_Cinema_Mode.user.js

// ==UserScript==
// @name        youtube/nicovideo Cinema Mode
// @description toggle on double click.
// @include     http://www.youtube.com/*
// @include     https://www.youtube.com/*
// @include     http://www.nicovideo.jp/watch/*
// @include     http://live.nicovideo.jp/watch/*
// @include     http://live.nicovideo.jp/gate/*
// ==/UserScript==

(function(){
	if(location.host.indexOf("www.youtube.com") === 0) {
		var css = '#masthead-positioner,#content,#footer-container,#watch-discussion{display:none!important;}'
				 +'body{background-color:#1B1B1B !important;}'
				 +'#player-api{position:static !important; margin:0 auto !important;}';
	} else if(location.host.indexOf("www.nicovideo.jp") === 0) {
		var css = '#siteHeader,#footer,#content > div:not(#playerContainerWrapper),#playerTabWrapper{visibility:hidden!important;}'
				 +'body{background-color:#1B1B1B !important;}'
				 +'#playerNicoplayer{margin:0 auto !important;}';
	} else if(location.host.indexOf("live.nicovideo.jp") === 0) {
		var css = 'body>div:not(#page_cover),#page>div:not(#slider_container):not(#watch_player_box),#wall,#utility_link{visibility:hidden!important;}'
				 +'body,#page_cover,#wall_canvas{background-color:#1B1B1B!important;}'
	}
	var style = null;
	function toggle() {
		if(style) {
			style.parentNode.removeChild(style);
			style = null;
		} else {
			style = document.createElement('style');
			style.type = 'text/css';
			style.appendChild(document.createTextNode(css));
			document.head.appendChild(style);
		}
	}
	document.addEventListener('dblclick', toggle);
})();