function pressEngine(new_engine, old_engine) {
	var new_idbtn_top = 'top_btn_'+new_engine;
	var new_btn_top = getObject(new_idbtn_top);
	
	new_btn_top.style.background = 'url(images/BTN_'+new_engine+'_press.png) no-repeat center';
	
	var new_idbtn_bottom = 'bottom_btn_'+new_engine;
	var new_btn_bottom = getObject(new_idbtn_bottom);
	
	new_btn_bottom.style.background = 'url(images/BTN_'+new_engine+'_press.png) no-repeat center';
	
	var old_idbtn_top = 'top_btn_'+old_engine;
	var old_btn_top = getObject(old_idbtn_top);
	
	if (old_btn_top){
		old_btn_top.style.background = 'url(images/BTN_'+old_engine+'_normal.png) no-repeat center';
		
		var old_idbtn_bottom = 'bottom_btn_'+old_engine;
		var old_btn_bottom = getObject(old_idbtn_bottom);
		
		old_btn_bottom.style.background = 'url(images/BTN_'+old_engine+'_normal.png) no-repeat center';
	}
}

function isBtnActive(btn){
	
	var reg = new RegExp(/(.*?)(press)(.*?)/);
	var str = btn.style.background;
	
	return str.match(reg);
}