//初期設定
var currentBlock="c0";//現在表示中のブロック
var opacityValue=1;//現在の透明度
var step=0.1;
var timer;

//フェード開始用
function fadeStart(block){
	if(!timer){
		timer=setInterval("fadeout('"+block+"')",1);	
	}
}

//フェードアウト
function fadeout(block){
	if(opacityValue>=0.05){
		opacityValue-=step;
	}
	else{
		opacityValue=0;
		clearInterval(timer);
		document.getElementById(currentBlock).style.display="none";
		currentBlock=block;
		document.getElementById(currentBlock).style.display="block";		
		timer=setInterval("fadein()",1);	
	}
	blockOpacity();
}
//フェードイン
function fadein(){
	if(opacityValue<=1){
		opacityValue+=step;	
	}
	else{
		opacityValue=1;
		clearInterval(timer);
		timer=undefined;
	}	
	blockOpacity();
}

//透明度を設定
function blockOpacity(){
	document.getElementById(currentBlock).style.opacity=opacityValue;
	document.getElementById(currentBlock).style.MozOpacity=opacityValue;
	document.getElementById(currentBlock).style.filter="alpha(opacity="+opacityValue*100+")";	
}