a.YT_btn {
	display: inline-block;
	/cursor: pointer; 
	position: absolute; 
	top:10px; 
	left:10px; 
	width:250px; 
	height:50px
	z-index: 100;
	/background-color: #007bff;
	/background-image: url("/img_YT/slide-YT-button3.png");
	background-image: url("/img_YT/slide-YT-button_N2.png");
}

@keyframes zmiana {
    0%   { background-image: url("/img_YT/slide-YT-button_N2.png"); }
	100% { background-image: url("/img_YT/slide-YT-button3.png"); }
					}

a.YT_btn:hover {
	display: inline-block;
	/width:250px; 
	/height:50px
	/z-index: 101;
	animation: zmiana; /* 1 sekunda, nieskończenie */
	animation-duration: 1s;
	background-image: url("/img_YT/slide-YT-button3.png");
}