var	challenge_ttl	= document.getElementById ('challenge_ttl');
var	challenge_txt	= document.getElementById ('challenge_txt');

for (var x = 4; x--; ) if (ch = document.getElementById ('challenge_img_' + (x + 1)))
{
	ch.catID	= x;
	ch.src_b	= ch.src;
	ch.src_o	= ch.src.replace (/(\.[a-z]+)$/i, '_o$1');

	ch.onmouseover	= function ()
	{
		this.src						= this.src_o;

		challenge_ttl.innerText = challenge_ttl.textContent	= catTtls[this.catID];
		challenge_txt.innerHTML					= catTxts[this.catID];
	};

	ch.onmouseout	= function ()
	{
		this.src						= this.src_b;
	}
}