平面CSS3菜单图像淡入淡出

我想知道如何才能让这个菜单在这里淡出背景图像，所以基本上打开从透明图标到透明文本的滚动请不要jQuery。这在CSS3飞机上可能吗

可以设置图标的活动链接，但不透明度为50%吗

有人能帮我吗？谢谢

CSS

.home {
    display: inline-block;
    position: relative;
    text-indent: -9999px;
    width: 170px;
    height: 112px;
    background: url(../images/qui_menu.png) no-repeat;
    background-position: 0px 0px;
}

.home span {
    position: absolute;
    top: 0; left: 0; bottom: 0; right: 0;
    background: url(../images/qui_menu.png) no-repeat;
    background-position: 0px -112px;
    opacity: 0;
    -webkit-transition: opacity 0.5s;
    -moz-transition:    opacity 0.5s;
    -o-transition:      opacity 0.5s;
}

.home:hover span {
    opacity: 1;
}

.services {
    display: inline-block;
    position: relative;
    text-indent: -9999px;
    width: 170px;
    height: 112px;
    background: url(../images/qui_menu.png) no-repeat;
    background-position: -170px 0px;
}

.services span {
    position: absolute;
    top: 0; left: 0; bottom: 0; right: 0;
    background: url(../images/qui_menu.png) no-repeat;
    background-position: -170px -112px;
    opacity: 0;
    -webkit-transition: opacity 0.5s;
    -moz-transition:    opacity 0.5s;
    -o-transition:      opacity 0.5s;
}

.services:hover span {
    opacity: 1;
}

.portfolio {
    display: inline-block;
    position: relative;
    text-indent: -9999px;
    width: 170px;
    height: 112px;
    background: url(../images/qui_menu.png) no-repeat;
    background-position: -340px 0px;
}

.portfolio span {
    position: absolute;
    top: 0; left: 0; bottom: 0; right: 0;
    background: url(../images/qui_menu.png) no-repeat;
    background-position: -340px -112px;
    opacity: 0;
    -webkit-transition: opacity 0.5s;
    -moz-transition:    opacity 0.5s;
    -o-transition:      opacity 0.5s;
}

.portfolio:hover span {
    opacity: 1;
}

.contacts {
    display: inline-block;
    position: relative;
    text-indent: -9999px;
    width: 170px;
    height: 112px;
    background: url(../images/qui_menu.png) no-repeat;
    background-position: -510px 0px;
}

.contacts span {
    position: absolute;
    top: 0; left: 0; bottom: 0; right: 0;
    background: url(../images/qui_menu.png) no-repeat;
    background-position: -510px -112px;
    opacity: 0;
    -webkit-transition: opacity 0.5s;
    -moz-transition:    opacity 0.5s;
    -o-transition:      opacity 0.5s;
}

.contacts:hover span {
    opacity: 1;
}