lightningforchimps.js

var CHANCE_OF_LIGHTNING = 1 / 100; // Tweak this.
var TOTAL_FRAMES = 4; // Include 'still' frame and lightning frames.

this.stop();
this.addEventListener('tick', function()
{
	if (Math.random() < CHANCE_OF_LIGHTNING)
	{
		this.gotoAndStop(Math.floor(Math.random() * (TOTAL_FRAMES - 1)) + 1);
	}
	else
	{
		this.gotoAndStop(0);
	}
});