Vapor Strobes

vaporstrobes-34539d25-662b-4891-877a-706e35258457@scriptish.user.js

// ==UserScript==
// @id             vapor.strobes-34539d25-662b-4891-877a-706e35258457@scriptish
// @name           Vapor Strobes
// @version        1.0
// @namespace      to.tumblr.com
// @author         to
// @include        *
// @run-at         document-end
// ==/UserScript==

var SHUT_TIME = 50;
var MAX_INTERVAL = 3000;
var SLICE = 25;

var intervals = [];
for(var i=SLICE ; i>=0 ; i--)
	intervals.push((Math.pow(i / SLICE, 3) * MAX_INTERVAL | 0) + 40);

[].push.apply(intervals, intervals.slice(0).reverse());

var shutter = document.createElement('div');
var style = shutter.style;
with(style){
	top = 0;
	bottom = 0;
	left = 0;
	right = 0;
	position = 'fixed';
	background = 'black';
	margin = 0;
	zIndex = 9999999999;
	pointerEvents = 'none';
	visibility = 'hidden';
}

document.documentElement.appendChild(shutter);

var interval;
var index = 0;
(function shut(){
	interval = intervals[index];
	index = (index + 1) % intervals.length;
	
	setTimeout(function(){
		style.visibility = 'visible';
		
		setTimeout(function(){
			style.visibility = 'hidden';
			
			shut();
		}, SHUT_TIME);
	}, interval);
})();